OBJECTIVES
Grades 5 – 8
°Become familiar with the microscope and its proper use.
°Prepare wet mount plant and animal slides.
°Observe prepared slides.
°Study diffusion and osmosis using dialysis tubing.
°Observe the stages of mitosis and understand that nuclear division is an important part of the cell cycle.

Grades 9-16
°Prepare slides and study the response of plants to changes in their osmotic environment.
°Examine a mite that is a normal inhabitant of human hair follicles.
°Observe stomates in the lower epidermis of a leaf and use counts of stomates in order to estimate the number in the entire leaf.
°Calculate the time needed for one cell cycle. The learner will understand cell growth and reproduction that occurs through mitosis and cytokinesis.

SCIENCE PROCESS SKILLS
Observing
Comparing
Inferring
Questioning
Applying
Hypothesizing
Collecting/Analyzing data
Logical thinking
Modeling
Writing scientifically
Designing an experiment
Forming conclusions

AAAS SCIENCE BENCHMARKS
5A Diversity of Life
5CCells
6CBasic Function

STATE SCIENCE CURRICULUM FRAMEWORKS
Grades 5 – 8
4.1.9Describe similarities/differences between single celled and multi- celled organisms.
4.1.10Explain how cells use food as a source of energy.
1.1.13Generate conclusions based on evidence.

Grades 9-12
2.1.15Analyze how scientific technology provides new tools for solving problems in all disciplines.
4.1.20Describe and explain the complexity of cellular structure and function (i.e., organelles, biochemistry, metabolism, photosynthesis, membrane functions, cell division).

SCIENCE EDUCATION STANDARDS (NCR)
Grades 5 – 8
Structure/Function in Living Systems
Reproduction and Heredity
Populations and Ecosystems
Diversity and Adaptations of Organisms

Grades 9-12
The Cell
HeredIty
Matter, Energy, Organization of Living Systems
Evolution of Living Systems
Biosphere and Interdependence

MATERIALS
Compound light microscope
Water source
Prepared animal and plant cell slides
Methylene blue stain
Toothpicks
Microscope slides
Covers lips
Droppers
Microscopes
Paper towels
Microscope immersion oil or mineral oil
Cardboard sheet or stiff index card
Oil of clove
Geranium plant leaves
15 cm plastic ruler
Dialysis tubing
20 cc syringe
15% glucose/2% starch solution
(15 grams of glucose, 2 grams of starch and 100 ml of water).
(This is enough solution for six groups.)
Iodine solution
(90 ml of water and 4 ml iodine)
Glucose testape
Plastic cups (large enough to hold 250 ml of water)
Triple beam balance
Salt solutions: 10% NaCl
Distilled water
Living Elodea leaves

KEY QUESTIONS
1.How are cells structured?
2.Explain how cells grow and divide.
3.What is the mechanism for cellular reproduction?
4.How do diffusion and osmosis differ?
5. What is dialysis?
Activity 1- Microscope use [The instructor should demonstrate as the students practice.]

Care of the Microscope
1.Carry the microscope in an upright position, one hand under the base, the other hand around the arm.
2.Do not permit excess electrical cord to dangle; leave some of the cord wrapped around the microscope.
3.Clean the lenses each time you use the microscope. Always use lens paper.
4.Report any difficulties with the microscope to the instructor.
5.Do not remove any part(s) of the microscope.
6.Do not allow the objective lens to strike the stage or slide/coverslip. 7.To store the microscope:
A.Turn nosepiece to the lowest power objective.
B.Wrap the cord around the microscope.
C.Cover.

Identification of Microscope Parts Using the table and the microscope diagram that follows, find and try out the various parts.
PartNameJob or Function
Aeyepiece/ocularholds top lens, usually lOx magnification through which object is viewed
Bbody tubesholds top lens, connects eyepiece to
objectives
Carmsupports body tube, a handle for carrying
Dnosepieceholds the objective lenses, turns to specific
objective
Ehigh powerobjective contains lens usually 40x, longest objective
on the nose iece, greatest detail
Fmedium power objectivecontains lens usually lOx, medium length if
3 objects are present, greater detail
Glow objectivecontains lens usually 4x, shortest length to
locate some detail
HCoarse adjustment moves body tube or stage up and down,
IFine adjustmentThe only adjustment used with high power.
JStageSupports the slide
Kstage clipsholds the slide in place
Ldiaphragm iris or diskcontrols the amount of light that enters the
microscope
Mlight sourceelectric lamp that provide the light into the
microscope
Nbasesupports the microscope, and used when
you carry the microscope
Ostage opening/apertureallows light to enter into the objectives

Use of the Microscope when using the microscope for the first time:
1.Turn on the microscope.
2.Look through the eyepiece. The cicle of light you see is called the field of view. Turn the diaphragm as you look through the eyepiece. You should notice that the light gets brighter or dimmer. Adjust the diaphragm with each specimen to determine the be st setting for that specimen.
3.Turn the nosepiece to change the objective lens. You should feel and/or hear a click as the objective is moved into place. Always start with the lowest power objective.
4.With a monocular microscope only one eye is used. Learn to work with both eyes open. If you have difficulty, hold your hand over one eye. It will be easiest to look through the microscope with your dominant eye.
5.The compound light microscope combines the magnifying power of two lenses. Total magnification equals the eyepiece magnification times the objective magnification. (eyepiece) x (objective) = total magnification. The eyepiece is usually lOX, the objectiv es are usually 4x, lOX, and 40X

The following procedure should always be used when observing any specimen under the microscope:

1.Start with the lowest power objective. Lower it as far as it will go.
2.Place the slide, prepared or temporary, on the stage. Be sure to use a cover slip.
3.Center your specimen over the stage- aperture. Raise the stage while looking through the eyepiece until you see the blurry image of the specimen.
4.Adjust the coarse focus, then fine tune with the fine focus. Remember to use the coarse focus only on low power.
5.Switch to medium power, adjust with the fine focus. Parfocal microscopes can switch directly from one objective to another without danger of hitting the slide.
6.Switch to high power, adjust the fine focus.

Making a temporary wet-mount slide (Figure 1)
1.Place a drop of water on a clean slide.
2.Place the specimen in the drop of water.
3.Position a cover slip at an angle over the specimen and gently lower into place.
4.Place slide on microscope stage and examine under low power.

Questions
a.why should you use a wet mount slide when viewing living cells?
b.why should the coverslip be lowered gently at an angle rather than being dropped on top of the specimen to be viewed?

Hints for Successful Microscope Observations
PROBLEMSOLUTION
Field of vision appears blackCheck to be sure that objective has clicked into position
Image appears fuzzy or unclearCheck eyepiece. Rotate it. Clean if
necessary.
Dirty eye iece or objectiveClean it.
Inability to locate specimenLower magnification. Recenter
specimen
Lack of sharp imageCheck to see that cover slip is on top
of slide
Too much or not enough light intensityAdjust diaphragm.
EyestrainObserve with both eyes open.
Out of focusAdjust focus frequently.
Inadequate observationScan all preparations by moving slide from side to side and up and down.

1.Place a drop of solution (stain, distilled, or salt water, etc.)
2.On the other side of the cover slip, put a piece of paper towel under the cover slip.
3.Allow the paper towel to draw the excess from under the cover slip.

Rules for microscope drawings
1.Pencil with shading or natural color with colored pencils.
2.Unlined paper, use one side only, leave at least a one inch margin on all sides.
3.Print all labels.
4.Three to four drawings per page maximum.
5.Draw and label only what you see through the microscope.

Pulling solutions across a wet-mount slide (Figure 2)
Activity 2- Cell observation

Materials
Paper towels
Coverslips
Eyedroppers
Microscope slides
Probes
Razor blades
Toothpicks
Unlined paper
Food coloring
Cork and/or bamboo
Methylene blue stain
Two or more colors of threads
Purple and yellow onion
Pencils and/or colored pencils
IKI/iodine stain
Assorted prepared slides such as:
Amoeba, paramecium, euglena, spirogyra, ulothrix, cholella, butterfly winds, insect eyes/mouth parts/legs, ox neuron, frog blood, etc.

Safety Considerations
°Breakage of glass slides and coverslips.
š IKI and methylene blue are toxins.
°Care should be taken in handling and using probes, razor blades, scissors, and toothpicks.
°Keep electrical connections dry and take care while plugging in or unplugging.

Procedures:
Make wet-mount slides of the following specimens. Observe them first on low power then on high power. Draw a representative cell on high power and label visible structures. Follow the directions given previously for making a wet-mount slide and for a dding solutions to a wet-mount slide.

1.Crossed Threads
Position two different colored threads (red, green) in an X on a clean slide. As you practice focusing note that because they are at different depths on your slide, both threads will not be in focus at the same time. This depth of field will also be n oticeable in cells viewed under the microscope.

2.Cork or Bamboo Cells
Shave a thin section from a piece of cork or bamboo, make a wet-mount slide and observe. A bottle cork, an old bamboo reed from a wind instrument, or fresh bamboo may be used. Note that in the dead cells, you will only see cell wall.

3.Onion Cells
Pull off the dry brown outer layer of a white or yellow onion and discard. Peel off a piece of the thin inner skin from between the thick layers of the onion and place it on a dean slide. Be careful to keep the tissue flat and in one layer. Put a drop of yellow food coloring or a drop of IKI (iodine) solution on the onion tissue. Wait a few seconds and blot the excess gently with a corner of paper towel. The cell and its structures will show up better after being stained. You should be able to see the cell wall, cytoplasm, and the nucleus. The cell membrane is directly inside the cell wall.
To see the cell membrane, compare fresh onion skin with onion skin that has been peeled off for around thirty minutes. The old onion will have dehydrated and the membrane and cytoplasm shrunk toward the center.

Questions
a.what differences do you notice between the unstained and stained slides?
b.what organelles, if any, can you see in the stained slide that you could not see in the unstained slide?

4.Purple onion
Repeat step three using a purple onion. Staining will not be necessary.

5.Cheek Cells
With the flat edge of a toothpick, gently rub the inside of your cheek. Smear the collected cell debris into a drop of water on a clean slide. Stain using methylene blue, iodine, or food coloring. You should be able to see the nucleus, cytoplasm, and cell membrane.

6.Stem Cross-Section
Slice as thin a section as possible from a fresh woody twig. Pace the section on a slide and observe it unstained, then stained with iodine, methylene blue or food coloring ring. Repeat with an herbaceous stem. You should be able to see various cells and tissue layers.

7.Prepared Slides
Observe various prepared slides (see materials list).

Typical Eukaryotic Cell Structures

Cell Parts

Nucleus
Nucleolus

Nuclear envelopes
pores
Chromosomes
Cell membrane

E.R.
smooth E.R
rough E.R.
Ribosomes
amino adds
Mitochondria
Vacuole
Vessicle
Lysosome
Golgi
Centriole

Microtubules
Chloroplast

Cell wall

Cytoplasm
Size (microns)

5-7
2

0.12-0.14
0.125
0.0024
0.006

0.01-0.08
0.01-0.08
0.01-0.08
0.025
0.0008
1.5-0.5
0.1
0.1
0.1
1-0.5
0.2-0.4

0.02-0.05
5.5-2

1-1.3

whole cell
Functions

šcommand center for cell activities and protein synthesis.
šproduces ribosomes and RNA
šregulateslates material entering and leaving nucleus.

šControls heredity
š controls materials entering and leaving cells
š lipid synthesis
šprotein synthesis
š protein synthesis
šbuilding blocks for protein
š cellular respiration produces energy from ATP

šstores water,minerals, food, waste

š membrane bound sac transports material

š garage collector in cell, cellular digestion

špackage material for export

šanimal cells only, microtubular organizing
center. i.e. Mitosis spindles and asters
šstructure and cytoplasmic streaming

š photosynthetic center of cell, contains chlorophyll. plant onl

šplant only, made cellulose
šmost cell activities occur
Activity 3
Observation of an animal living on the human skin: Follicle mites

Purpose
To examine a mite that is a normal inhabitant of human hair follicles.

Materials
Compound microscope
Two or more glass slides
Two or more glass cover slips
Toothpicks
Microscope immersion oil (or mineral oil)
A thin piece of cardboard (back of notepad, etc.)

Background Information
Animals come in all shapes and sizes. Some of the multicellular animals with complex and variously specialized organ systems are hardly larger than some of the one celled protozoans. Mites of the genus Demodex are closely related to the spiders and ticks, but are so small that they can live within the human hair follicle and feed on the follicular cells and the oils produced by the glands associated with the hair. The two species found on humans, D. folliculorum and D. brevis, do not commonly cause problems to their hosts, in fact, they are far less numerous in individuals with skin disorders such as acne. In some older people, D. folliculorum has been suspected of causing irritation and a reddening of the skin near the eye bro ws and lower forehead, painful but not severe. However, the related mite that occurs on dogs, D. canis, can cause demodectic mange, a rather severe skin condition. Numerous D. folliculorum may be found in a single follicle, but only one D. < I>brevis is found in an oil gland. Passage of mites from person to person is by direct contact.

Procedure

1.Clean a slide and cover slip. Place one drop of immersion oil or mineral oil onto the slide.

2.With one hand pull the skin of your forehead tight. Taking the card in the other hand press the edge of the card firmly against the skin and scrape it across your forehead. Remember, you are expressing oils and mites from the pores and follicles of the skin, so the firmer the pressure, the more likely you are to find mites. Best results are obtained by using the edge of a glass slide, but extreme care must be used to avoid breaking the slide and cutting yourself.

3.With the toothpick, remove the oily mass you have collected on your car and stir it into the drop of immersion oil on the slide. Place a cover slip over the drop.

4.Examine the slide under lOOX and change to 400X magnification when a suspected mite is observed. These mites are small, but easily seen under lOOX. The 400X is required only to examine the details of their structures.

5.It may be necessary to make more than one slide to determine how much pressure on the card is required to express the mites. However, everyone has some skin mites, so given patience, success should be virtually assured.

6.Good hunting!

To observe stomates in the lower epidermis of a leaf and to use stomatecounts under high power fields of view to estimate the total number in one leaf.

Activity 4- Gas exchange and photosynthesis

Purpose

Background Information
During photosynthesis CO2 and H2O are used as raw materials in the production of glucose. Light energy and enzymes are required in order for photosynthesis to occur. As water molecules are split providing electrons and H+ used in photosynthesis, oxyge n molecules are released. Most photosynthesis occurs in chIoroplasts in the mesophyll (middle) layers of the leaf. CO2 diffuses into the mesophyll region through stomata (small openings) in the leafs epidermal layers. Oxygen diffuses outward through th e stomates during photosynthesis. During periods of darkness with no photosynthesis and only cell respiration occurring, the direction of diffusion is reversed. Water diffuses into the mesophyll region from xylem cells in the veins providing a continuous flow of water from root hairs to the leaves. During any period when the stomates are open, water will diffuse outward from the leaf (transpiration). Opening and closing of stomata are controlled
In this activity, a portion of the lower epidermis will be removed from a leaf, and the stomates, with the surrounding guard cells, will be observed and counted. The total number of stomates in the lower epidermis of the entire leaf will be estimated from these counts.

Procedure
A.Number of Stomates
1. Tear a leaf at an angle while holding the lower surface upward. The tearing action should peel off a portion of the lower epidermis. It will appear as a narrow, colorless zone extending beyond the green part of the leaf.
2. Using forceps, tear off a small piece of this epidermis. immediately place it in a drop of water on a slide. Add a cover slip. Do not allow the fragment to dry out.
3. Using the low power objective of your microscope, locate some stomates. Then switch to the high-power objectives. Make a drawing to show the shape of a stomate, its guard cells, and a few adjacent cells in the epidermis.
4. Count the number of stomates in 5 high power fields of the microscope and average them. Calculate the average number of stomates per mm2 of leaf surface. This can be done by finding the diameter of the high power field of view and then computing the h igh power field of view area (area = r2). To find the high power diameter, divide the magnification number of the high power objective by that of the low power objective. Then divide the diameter of the low power field of view by this quotient. The resu lt is the diameter of the high power field of view.
5. Measure the total leaf surface area using cm2 grid paper and estimate the total number of stomates in the entire leaf.

Questions
1. What purpose do the guard cells serve?
2. What are the structures visible in the guard cells?
3. Why are there more stomates in the lower epidermis?
4. Can you think of a plant that would have more stomates in the upper epidermis than in the lower epidermis?
5. What plant types would be likely to have the fewest stomates?
Activity 5 – Diffusion and osmosis The life of a cell depends on movement of atoms and molecules. One of the results of this molecular motion is diffusion. Diffusion is the random movement of molecules from a place of higher concentration to a place of lower concentration. The concent ration of molecules at various points between the high and low areas forms a gradient, which is known as the concentration gradient.
Osmosis is the diffusion of water through a selectively permeable membrane. A selectively permeable membrane allows the diffusion of certain solutes and water molecules and restricts the movement of some solute molecules.
When comparing two solutions, the solution with the greater concentration of solutes is the hypertonic solution, while the solution with the lesser concentration of solutes is the hypotonic solution. when the two solutions are divided by a selectively per meable membrane, water molecules move from the hypotonic solution to the hypertonic solution. The solute molecules move from the hypertonic solution to the hypotonic solution. If the two solutions have the same concentrations of solutions are isotonic.

Background Information

Purpose
This activity is designed to observe diffusion and osmosis through a selectively permeable membrane (dialysis tubing). A selectively permeable membrane will allow substances to diffuse at different rates. The movement of a solute through a selectively permeable membrane is called dialysis.

Part A: Diffusion 1.Secretly place a drop of oil of clove in the front corner of the room.
2.Allow the aroma to diffuse through the room until students begin to notice the aroma and comment on it.

Procedure

Questions
1.What part of the room noticed the aroma first?
2.What part of the room noticed the aroma last?
3.Explain how the aroma moved through the room.
Part B: Dialysis

Procedure
All of the molecules of a given substance are about the same size, but the molecules of different substances are different in size. Iodine and water molecules are very small, glucose is larger and starch molecules are very large. A selectively permeable membrane allows some molecules to pass and restricts others. Design an experiment to show dialysis.

Materials
Dialysis tubing
20 cc syringe
15% glucose/2% starch solution
(15 grams of glucose, 2 grams of starch and 100 ml of water) (This is enough solution for six groups.)
Iodine solution (90 ml of water and 4 mi iodine)
glucose testtape
Plastic cups (large enough to hold 250 mL of water)
Water
Triple beam balance

Procedure
1.Using glucose testtape, test the glucose/starch solution. Record the results in the data table.
2.Cut a 30 cm length of dialysis tubing. Soak the tubing in a cup of water for five minutes. Remove the tubing from the water and tie one end.
3.Using the 20 cc syringe, place 15 ml of the glucose/starch in the dialysis bag. Tie the other end of the dialysis bag leaving enough space for expansion.
4.Record the color of the liquid in the bag in the data chart. Mass the bag and record the mass in the data table.
5.Mix 90 ml of water and 4 ml of iodine in a cup. Using glucose testtape, test the iodine solution and record the results in the data table.
6.Mass the cup and its contents. Record the mass in the data table.
7.Place the dialysis bag in iodine-water mixture and allow the setup to stand for thirty minutes. After thirty minutes, remove the dialysis bag from the iodine-water solution. Drain as much of the liquid as possible from the outside of the bag back into t he cup. Blot the dialysis bag dry on a paper towel. Mass the dialysis bag and record the results in the data chart.
8.Mass the cup and iodine solution. Record the results in the data chart.
9.Observe the color of the contents of the dialysis bag and the cup and record this information in the data table.
10.Using glucose testtape, test the liquid in the dialysis bag and in the cup and record the results in the data table.
11.Calculate the percent change in mass of the dialysis bag and of the cup (% Change in mass = (Final mass – Initial mass)/Initial Mass x 100).
Note:If water enters the bag, there will be a positive value for % change in mass. If water leaves the bag, there will be a negative change in mass. The same will be true for the cup.
DATA TABLE

InitialInitialFinal% ChangeFinal
ContentsColorMassTestapeColor
MassTestapeIn MassContents

Bag

Cup
Questions
1.Which substance(s) are entering the dialysis bag and which are leaving the bag? What evidence do you have to support this answer?
2.Which substance(s) did not pass through the membrane? Give supporting evidence for your answer.
3.Did water move in this experiment? What evidence do you have for the movement?
4.Referring to your experiment, were you correct? If you were incorrect, rewrite it to account for your observations.
5.Was the dialysis bag selectively permeable? Give evidence to support your answer.
6.Predict the effect of temperature on your experiment of…

Increasing the temperature:
Decreasing the temperature:
 To examine the response of plants to changes in their osmotic environment.

Activity 6- Membrane responses of living organisms

Purpose

Materials
Compound microscope
Slides and cover slips
Salt solutions 10% NaCl
Distilled water
Living Elodea leaves

Background Information:
In a healthy plant cell, isotonic with its environment, the cytoplasm, chIoroplasts, and other cell organelles are pressed against the rigid cell wall by a large central vacuole filled with water applying turgor pressure to the contents. The size of the central vacuole changes as water passes into or out of the cell in response to differing environmental conditions. when the plant is in a dry environment, the fluid outside the cell becomes more concentrated (hypertonic) than the cytopla sm, water passes out of the cell by osmosis, the vacuole becomes smaller, and the cytoplasm shrinks away from the cell wall. This process of cell shrinkage in plants is called plasmolysis. The combined shrinkage of all the plant’s cells cause it to appear wilted. when water is taken up by the plant, the fluids outside the cell become more dilute than the cytoplasm and water enters the cell, the vacuole increases in size, the cytoplasm becomes pressed against the cell wall by increased turgor pressu re, and the plant regains its unwilted shape. Since the central vacuole is the first cellular structure to gain or lose water, its size and effect on the positions of other cellular structures can be used as in indicator of the osmotic conditions with the plant cell.

Procedure
1.Make a temporary wet amount of an Elodea leaf using water from the plant’s container.
2.Cover with a cover slip and observe the distribution of cellular structures (chIoroplasts will be particularly visible) under low and then high power. Best results will be obtained in the thin area where the leaf was torn from the plant.
3.Place a drop of 10% salt solution on the side of the cover slip. On the other side of the cover slip, put a piece of paper towel under the cover slip (See Figure 2 in Activity 1). Allow the paper towel to draw the salt solution under the cover slip by c apillary action Observe the distribution of the chloroplasts as before. If no change occurs within a few minutes add another drop of 10% salt solution and draw it under the cover slip as before. Continue to observe the cells for up to 15 minutes.

Questions
1.Why do we use water from the plant’s container?
2.What changes would you expect to observe? what do you observe? Explain the results.
3.Is the 10% salt solution hypertonic or hypotonic to cellular contents?

Procedure
4.Place a drop of distilled water at the edge of the cover slip and draw it under the cover slip by capillary action, as before. Continue to add distilled water while observing the cells for changes in vacuole size for up to 15 minutes.

Questions
1.How is the salt concentration of the medium surrounding the leaf?
2.What do you expect to observe in the cells? what do you observe? Explain.

Activity 7- The cell cycle To identify cell cycle stages and estimate the time needed for one cell cycle.

Purpose

Background Information
The cell cycle includes both the period of time for the division of the nucleus (mitosis) and the period of time for cell growth and chromosome duplication. Interphase is the cell cycle stage between mitotic divisions during which cell growth and chromosome duplication occurs. Mitosis includes four cell cycle stages: prophase, metaphase, anaphase, and telophase. During prophase, the chromosomes become distinguishable as they condense. A spindle forms, and the nuclear membrane br eaks down. During metaphase, the chromosomes become arranged near the center of the cell. The chromatids of the chromosomes separate and move to opposite ends of the cell in anaphase. Cell division is completed in telophase as the cy toplasm divides (cytokinesis), the nuclear membrane reforms, and the two daughter cells separate.
Cell division in plants occurs in meristem tissue located in buds, cambium, and root tips. Of these regions of growth, the greatest number of dividing cells can be seen at the root tip. You will observe sections of Allium (onion) root tip. Toward t he main plant body the cells have grown to full length and are no longer dividing. Near the root tip, however, is the root apical meristem, a region of rapid cell division. Among the small cells of the root meristem you should be able to find cells in all stages of the cell cycle.
Unllke plants, which grow only in certain areas, animal growth occurs in various tissues throughout the body. Some cells in the human body are continuous replicators or are cell populations that continuously run the cell cycle. Examples of continuous repl icators would be skin, gastrointestinal lining, bone marrow, and hair follicles.
Some other cell types become incapable of continued cell division and are called non-replicators. Examples of these types of cells would be brain cells, heart muscle cells, and skeletal muscle cells.
A third class of cells are the occasional replicators. These cells normally do not undergo cell cycle but are capable if stimulated to do so. The most popular example of this kind of replicator is the liver cell. Liver cells normally do not divide. Howe ver, if part of the liver is surgically removed, the “stump” can regenerate the missing part by the re-initiation of the cell cycle in the “stump” liver cells. The cell cycle continues until there is complete replacement of what was surgically removed. As an animal matures, its rate of cell division declines; therefore, cell division is most common in embryos shortly after fertilization. For these observations, use a prepared slide of a whitefish blastula (a blastula is an early stage in development). A t this stage, the embryo is largely a mass of dividing cells. Four slices of about one hundred cells each were placed on each slide and stained. Among these sections you can find cells in all of the stages of the cell cycle.

Part A: Identification of the mitotic phases

Procedure

1.Using the Allium root tip slide, locate, sketch, and label cells in interphase, prophase, metaphase, anaphase, and telophase. Also notice the manner of cytokinesis, i.e., the formation of a new cell wall, called a cell plate, between the t wo new nuclei.
2.Using the whitefish blastula slide, locate, sketch, and label cells with nuclei in interphase, prophase, metaphase, anaphase, and telophase.

Part B: Calculation of cell cycle time
The chemical colchicine stops nuclear divisions at metaphase, but affects no other stage of the cell cycle. This can be used in attempts to determine the time needed for a full turn of the cell cycle. This can be used in attempts to determine t he time needed for a full turn of the cell cycle. First, the percentage of nuclei in metaphase of untreated tissue is determined (This value is about 1%). Living material is then treated for a specific time of 30 minutes (T) with colchicine. Slides of t he colchicine treated material are prepared, and again the percentage of metaphase nuclei is determined. The change in percentage over this specific time (T) relates to the overall time of the cell cycle as follows:

_____ % metaphase (colchicine treated cells)

_____-1% metaphase (normal cells)
=Q
T(time) = Q % of total cycle

Therefore, T/Q % = time of entire cell cycle

For example, if cells were treated for 30 minutes and (% treated) – (% normal) = 20%, then T/Q = 30 min/0.20 = 150 minutes for the entire cell cycle.

Procedure
1.The slides available in lab are of onion root tips treated for 30 minutes with colchicine. In normal tissue the percentage of nuclei in metaphase would be 1%. Two students work together, one as an observer and one as a recorder. The observer ranges up and down three central vertical rows of cells visible within the field at one time and identifies the cell cycle stage for each cell. The recorder records the data in the table below. Four such field counts should be made, with the observer and recorde r changing roles alter the second count. It is suggested that only the three most central rows be counted in each field.

Field Count

Phase1234Totals

prophase
_______________________________________________________________

metaphase
_______________________________________________________________

anaphase
_______________________________________________________________

telophase
_______________________________________________________________

interphase
_______________________________________________________________

Sum of all totals = ______ 2.Now divide the total of all metaphase cells by the total of all phases combined. This gives the percentage of 30 minute colchicine treated cells in metaphase. From this, subtract 1%, the percentage of untreated cells in metaphase. The normal length of the cell cycle can be calculated as shown above.

The length of the cell cycle for onion root tip cells is ___________

• The human genome contains 3 billion chemical nucleotide bases (A, C, T, and G).
• The average gene consists of 3000 bases, but sizes vary greatly, with the largest known human gene being dystrophin at 2.4 million bases.
• The functions are unknown for more than 50% of discovered genes.
• The human genome sequence is almost (99.9%) exactly the same in all people.
• About 2% of the genome encodes instructions for the synthesis of proteins.
• Repeat sequences that do not code for proteins make up at least 50% of the human genome.
• Repeat sequences are thought to have no direct functions, but they shed light on chromosome structure and dynamics. Over time, these repeats reshape the genome by rearranging it, thereby creating entirely new genes or modifying and reshuffling existing genes.
• The human genome has a much greater portion (50%) of repeat sequences than the mustard weed (11%), the worm (7%), and the fly (3%).
• Over 40% of the predicted human proteins share similarity with fruit-fly or worm proteins.
• Genes appear to be concentrated in random areas along the genome, with vast expanses of noncoding DNA between.
• Chromosome 1 (the largest human chromosome) has the most genes (2968), and the Y chromosome has the fewest (231).
• Genes have been pinpointed and particular sequences in those genes associated with numerous diseases and disorders including breast cancer, muscle disease, deafness, and blindness.
• Scientists have identified about 3 million locations where single-base DNA differences occur in humans. This information promises to revolutionize the processes of finding DNA sequences associated with such common diseases as cardiovascular disease, diabetes, arthritis, and cancers.

genome-initial studies

A Brief Overview

Though surprising to many, the Human Genome Project (HGP) traces its roots to an initiative in the U.S. Department of Energy (DOE). Since 1947, DOE and its predecessor agencies have been charged by Congress with developing new energy resources and technologies and pursuing a deeper understanding of potential health and environmental risks posed by their production and use. Such studies, for example, have provided the scientific basis for individual risk assessments of nuclear medicine technologies.

In 1986, DOE took a bold step in announcing the Human Genome Initiative, convinced that its missions would be well served by a reference human genome sequence. Shortly thereafter, DOE joined with the National Institutes of Health (NIH) to develop a plan for a joint HGP that officially began in 1990. During the early years of the HGP, the Wellcome Trust, a private charitable institution in the United Kingdom, joined the effort as a major partner. Important contributions also came from other collaborators around the world, including Japan, France, Germany, and China.

Ambitious Goals

The HGP’s ultimate goal was to generate a high-quality reference DNA sequence for the human genome‘s 3 billion base pairs and to identify all human genes. Other important goals included sequencing the genomes of model organisms to interpret human DNA, enhancing computational resources to support future research and commercial applications, exploring gene function through mouse-human comparisons, studying human variation, and training future scientists in genomics.

The powerful analytic technology and data arising from the HGP raise complex ethical and policy issues for individuals and society. These challenges include privacy, fairness in use and access of genomic information, reproductive and clinical issues, and commercialization (see p. 8). Programs that identify and address these implications have been an integral part of the HGP and have become a model for bioethics programs worldwide.

A Lasting Legacy

In June 2000, to much excitement and fanfare, scientists announced the completion of the first working draft of the entire human genome. First analysis of the details appeared in the February 2001 issues of the journals Nature and Science. The high-quality reference sequence was completed in April 2003, marking the end of the Human Genome Project—2 years ahead of the original schedule. Coincidentally, this was also the 50th anniversary of Watson and Crick’s publication of DNA structure that launched the era of molecular biology.

Available to researchers worldwide, the human genome reference sequence provides a magnificent and unprecedented biological resource that will serve throughout the century as a basis for research and discovery and, ultimately, myriad practical applications. The sequence already is having an impact on finding genes associated with human disease (see p. 3). Hundreds of other genome sequence projects—on microbes, plants, and animals—have been completed since the inception of the HGP, and these data now enable detailed comparisons among organisms, including humans.

Many more sequencing projects are under way or planned because of the research value of DNA sequence, the tremendous sequencing capacity now available, and continued improvements in technologies. Sequencing projects on the genomes of many microbes, as well as the honeybee, cow, and chicken are in progress.

Beyond sequencing, growing areas of research focus on identifying important elements in the DNA sequence responsible for regulating cellular functions and providing the basis of human variation. Perhaps the most daunting challenge is to begin to understand how all the “parts” of cells—genes, proteins, and many other molecules—work together to create complex living organisms. Future analyses on this treasury of data will provide a deeper and more comprehensive understanding of the molecular processes underlying life and will have an enduring and profound impact on how we view our own place in it.

DNA from all organisms is made up of the same chemical and physical components. The DNA sequence is the particular side-by-side arrangement of bases along the DNA strand (e.g., ATTCCGGA). This order spells out the exact instructions required to create a particular organism with its own unique traits.

The genome is an organism’s complete set of DNA. Genomes vary widely in size: the smallest known genome for a free-living organism (a bacterium) contains about 600,000 DNA base pairs, while human and mouse genomes have some 3 billion .Except for mature red blood cells, all human cells contain a complete genome.

DNA in the human genome is arranged into 24 distinct chromosomes–physically separate molecules that range in length from about 50 million to 250 million base pairs. A few types of major chromosomal abnormalities, including missing or extra copies or gross breaks and rejoinings (translocations), can be detected by microscopic examination. Most changes in DNA, however, are more subtle and require a closer analysis of the DNA molecule to find perhaps single-base differences.

Each chromosome contains many genes, the basic physical and functional units of heredity. Genes are specific sequences of bases that encode instructions on how to make proteins. Genes comprise only about 2% of the human genome; the remainder consists of non-coding regions, whose functions may include providing chromosomal structural integrity and regulating where, when, and in what quantity proteins are made. The human genome is estimated to contain 20,000-25,000 genes.

Although genes get a lot of attention, it’s the proteins that perform most life functions and even make up the majority of cellular structures. Proteins are large, complex molecules made up of smaller subunits called amino acids. Chemical properties that distinguish the 20 different amino acids cause the protein chains to fold up into specific three-dimensional structures that define their particular functions in the cell.

The constellation of all proteins in a cell is called its proteome. Unlike the relatively unchanging genome, the dynamic proteome changes from minute to minute in response to tens of thousands of intra- and extracellular environmental signals. A protein’s chemistry and behavior are specified by the gene sequence and by the number and identities of other proteins made in the same cell at the same time and with which it associates and reacts. Studies to explore protein structure and activities, known as proteomics, will be the focus of much research for decades to come and will help elucidate the molecular basis of health and disease.

It is evident that, a physiological mechanism allows the targeting and elimination of a sub-population of abnormal sperm- among mice, during fertilization.This mechanism, established by the sperm themselves, increases the chances of fertilization and reduces the risk of fertilization with a sperm defect. These results were published April 26, 2010 in the Journal of Clinical Investigation by researchers at the CNRS (National Centre for Scientific Research, better known by its initials, CNRS, ) and the Inserm, belonging to the Institute of Neuroscience (Neuroscience include all the sciences needed to study the anatomy and functioning of the system.) in Grenoble, in collaboration with Japanese researchers. Transposed to humans, they would select the best sperm for assisted reproductive technologies (LDCs) and increase the chances of having a child for infertile couples.

Approximately 15% of couples have infertility problems, half of which is due to deficiencies of man. Over the last thirty years, various techniques have been developed to meet the needs of infertile couples, and now in the industrialized nations, almost 2% of children born through assisted procreation (PMA). Despite this undeniable progress, many infertile couples unable to have children. Moreover, the risk to the world  a child with a rare genetic disease, although very low, is significantly higher in children born using the techniques of LDCs . Several reasons have been cited including a higher risk of selection defective sperm in the techniques of LDCs in relation to natural selection process. In this context , the choice gametes used is of particular importance: on what criteria should they be selected?

Team containing- Christophe Arnoult, CNRS researcher in the Institute of Neurosciences, Grenoble (Inserm Unit 836, University Joseph Fourier, Grenoble), Gerard Lambeau, CNRS researcher at the Institute of Molecular and Cellular Pharmacology (CNRS / University of Nice) and the team of Makoto Murakami (The Tokyo Metropolitan Institute of Medical Science, Japan) have recently shown, mice, the existence of a physiological mechanism that can target and eliminate a sub-population of sperm with abnormalities on their lipid component plasma membrane. Indeed, after their entry into the female genital tract, some sperm are released during maturation enzyme called phospholipase A2 group X secreted This destroys the acrosome (2) of abnormal spermatozoa, which makes them unable to fuse with the oocyte. They are thus rendered infertile and excluded from the ” race (Race: This word has several meanings, all related to the movement.) at fertilization.

The researchers conducted experiments to show that the absence of secreted phospholipase A2 group X (genetically modified animals or inhibition by specific antagonists) decreases the rate of fertilization and embryonic development alters. Conversely, if we add a high concentration of enzyme in a synthetic population of spermatozoa, we observed an increase in fertilization rate of 30% in a very fertile animal model (normal mice) and 100% in a model infertile animals (inbred mice in which the reproduction rate is very low). The enzyme can therefore effectively eliminate much of defective sperm.

These works reveal the “cooperative work” of sperm sorting themselves mutually to reduce defective sperm during fertilization. They also highlight the importance of the lipid membrane of the sperm into the mechanisms of sperm maturation and fertilization.

Researchers will now study the efficacy and safety of treatment of sperm by phospholipase A2 group X secreted in a primate model. Applications for the use of such molecules (phospholipase A2) in the context of assisted reproduction and contraception have been patented.

If their work is validated, then this discovery could allow humans to improve the techniques of medically assisted procreation (PMA). The quality of sperm membrane lipids could indeed be a new criterion used by practitioners who select sperm for these techniques. They could thus increase their efficiency, and therefore the chances of success, and help reduce the risk of birth defects among children born through the PMA.

This video explores how human clones are being made – for medical research. Arguments for and against human cloning research. Why some people want to clone themselves or even to clone the dead (and not just cloning pets).

Arguments For and Against Cloning

Here is a list of arguments that the most frequent in the debate for or against human cloning. Start not on the arguments in favor:

- Cloning could create a being identical to a child or a close relative died.

- It might be a technical support for infertile parents to single mothers, gay couples for invoking a right to the child.

- The cloning would offer the possibility of creating a child “therapy” can be used to provide a transplant.

- Cloning is a way to ensure immortality, an idea very much in common with cults.

- The positions of authority could be reserved for individuals Pre qualified to elites.

- The financial interests of cloning would be considerable, especially with the market for reproduction, the patent technology.

Now we will see the arguments against human cloning:

- The creation of a clone would be a process very expensive, therefore, a process that would not be usable by all.A  A‚

- Cloning could become a form of slavery as being clone is like any decision for him (her physical, character …).

- The twins have difficulty finding their identity, and cloning would have even more difficult because it would be a copy of a being that it removes all unique to each person.

- This way of reproduction abolish an essential about human lineage.

- The cloning would have genetic characteristics predetermined. These characteristics are the result of chance in sexual reproduction, it allows us to be different from each other. Human cloning would therefore against the mechanisms of evolution of life.

- The cloning could lead to slippage due to the very important economic issue that emerges.

It can therefore be noted that the arguments against human cloning are “high” for that. Indeed we can see that some argument is a disagreement with an ethic that would be protective of the human species. For some argument could be used almost as an argument against.

Pour therapeutic cloning there is a strong divergence of opinions.

The ethylamine is a carnivore of the sub-group of mammals that lived marsupials in Tasmania, south-eastern Australia. Despite its name, it has no connection with the wolves or any cat. Hunting and the introduction of alien species caused his death at the beginning of the century. Many specimens are nevertheless kept in museums.

This study was possible thanks to the Smithsonian Institution museum in the United States and the Museum of Natural History in Stockholm. Both institutions remain, in fact, specimens of the Tasmanian wolf who had lived in the zoo in Washington DC and London. The DNA analysis was performed on hair samples taken from these two specimens. The technique has achieved an average of 50 measurements per nucleotide, ensuring the fidelity of sequencing.

Comparing the genetic sequence of the two individuals showed differences in only 5 nucleotides in more than 15,000. This poverty measure of the genetic heritage of the wolf of Tasmania just before its extinction. This poverty is regarded as one of characteristics of endangered species. It in effect reduces the ability of resistance to new diseases or changing environment. Scientists have also conducted an analysis of organisms in the samples. This allowed, firstly, to ensure that the sequenced DNA originated from the species studied, on the other hand, give an evaluation of conservation measures. It was indeed found significant differences between the microbial fauna of the two specimens studied.

This study demonstrates the feasibility and utility of sequencing DNA from museum specimens. The authors also hope to soon reach full sequencing.

Source: http://www.uu.se/press/pm.php?id=453

The good old computing center under the super control specialists in white coats, and many terminals are attached. Believe how such a setback, after the apparent release of micro-computers, his incredible sense of autonomy, with the added commitment that you wear to be (almost live) to be taken care, fear its heat stroke, make sure its clean, shown to grow with you, update after update. In fact, no need to believe, as we saw already.

We have not paid attention too early, for example with the web mail and with shared files on the intranet, but also with phone numbers that may keep our mobile without a SIM card, or now with the texts cooperative that can be edited several (electronic bulletins ADIT). The ecosystem of computing is evolving at great speed at this time, accelerated by the financial crisis.

First observation: even at the price of a migration to cheap contracts, such as “pay-as-you-go”, the mobile phone market has not collapsed (figures 2008). Personal information that it creates tend to increase (address books, calendars, images, messages) and the proposed applications tend to reach the rank of substitute computer.

Second observation: the sales of desktops, for against, have collapsed, and those laptops are significantly low. The only sector that has grown is the “netBook, ie the” Notebook “(a term given to laptops, alleviated some services less expensive and designed primarily for office) oriented to use a large majority on the net. In the context of virtualization, the netBook can be further alleviated (fi readers CD / DVD) and even their operating system becomes a lightweight, almost the size of a portable telephone system. It should be noted, also because of the price argument, that the percentage of NETBOOK Linux is much higher than the percentage of that Linux, with their big cousins laptops. So today, the model with OS free NETBOOK reached the ceiling price of $ 200 and can expect to see even lower soon. The beautiful project , from MIT’s laptop for children in emerging countries, to $ 100 (but $ 400 in developed) countries, is likely to disappear with the company seeking to market it. Not a failure on the merits: they have been double by the evolving market. This is a new economic model of personal computing that is being established. Bluf stroke or not, an Indian company announces laptop to $ 20. When the laptop Disposable, as the camera of the same name?

In this landscape, all of the information industry and telecommunications are faced with crucial choices. Wrenching and very binding for Microsoft, these choices are smiling for the giant blue that we thought moribund IBM reigned without sharing the computing centers of the 1960s. The situation is not catastrophic for the telecom companies, or those who, like Apple, they took the turn of the iPhone.

What are these choices? it’s the cloud, stupid! On one side of the small computers, light in all senses of the term, prices, weight and integrated software, and much more rich applications and capabilities exchange. At the other end (the high-end computing), the huge computer centers, the “farms” of thousands of powerful computers, very hot and very hungry, but that no one visit, because we often ignore when they are . And these data centers, or as data centers, because that is what it is above all, are intended to capture any home.

When we said capture, it must be read. Your files, your images, your address, your most intimate details, your passwords, your time entered in your calendar, but also the intimate details of your companion for life that was your personal computer. Most need of operating system, need more data as soon as you connect (yes agree we need a very small operating system for this) and you are identified, all of this is provided by the cloud. Want to print? the cloud with your favorite printer and take care of everything. You want updates? Why, the cloud has already occupies.

Performance, you say? But who better than the cloud, can balance the use of bandwidth, distributed caching of data, share the same bits of information that were previously duplicated among all employees of the same hotel? Data security, protection against viruses? but the cloud is there, who watches 24/24, 7 / 7, to track the virus, with versions of anti-virus up to date in the hours of their broadcast. I say that the hour, minute, second. Protection against theft? it was stolen, or you lost your laptop between Paris and LA? No worries, Mr. Cloud is going to report as soon as someone indelicate power on your computer: it will be blocked and if you requested the same data on your hard disk physically in-your-laptop will be erased . Remember that tape of that grid spy tapes? The fiction has become reality.

Here is some of the responses that companies like VMware and Cisco can make to their customers or prospective customers, today. Microsoft is no exception, which is recycled at high speed. Privacy? the guarantee that my data will remain confidential, secret selves? Uh, it starts to be late for questions, but you think about it.

That is essentially what was said at the conference held on February 4 at Pentagon City. We will therefore privacy, as we talk of calories generated by large hosts.

Conclusion: If “small is-still-beautiful, the beautiful big returns, but you are asked to say” the cloud is beautiful. “

Source:Â http://www.youtube.com/watch?v=6PNuQHUiV3Q