Biology Junction Team - BIOLOGY JUNCTION

Mitosis and Meiosis

Mitosis and Meiosis

Introduction
All new cells come from previously existing cells. New cells are formed by the process of cell division which involves both replication of the cell’s nucleus (karyokinesis) and division of the cytoplasm( cytokinesis).

There are two types of nuclear division: mitosis and meiosis. Mitosis typically results in new somatic (body ) cells. Formation of an adult organism from a fertilized egg, asexual reproduction, regeneration, and maintenance or repair of body parts are accomplished through mitotic cell division. Meiosis results in the formation of either gametes (in animals) or spores ( in plants). These cells have half the chromosome number of the parent cell. You will study meiosis in Exercise 3B. Where does one find cells undergoing meiosis? Plants and animals differ in this respect. In higher plants the process of forming new cells is restricted to special growing regions called meristems. These regions usually occur at the tips of stems or roots. In animals, cell division occurs anywhere new cells are formed or as new cells replace old ones. However, some tissues in both plant and animals rarely divide once the organism is mature.

Exercise 3A.1: Observing Mitosis in Plant and Animal Cells Using Prepared Slides of the Onion Root Tip and Whitefish Blastula

Figure 3.1 Close up view of different stages of mitosis in an onion root tip:

Figure 3.2 Whitefish Blastula

Procedure:
Examine prepared slides of either onion root tips or whitefish blastula. Locate the meristematic region of the onion, or locate the blastula with 10X objective, and then use the 40X objective to study individual cells. Identify one cell which clearly represents each phase of mitosis. Sketch and label the cell in the box provided.

1. The non dividing cell is in a stage called interphase. The nucleus may have one or more dark-stained nucleoli and is filled with a fine network of threads, the chromatin. During interphase, DNA replication occurs.

Interphase

2. The first signs of cell division occurs in prophase. There is a thickening of the chromatin threads, which will continue until it is evident that the chromatin has condensed into chromosomes. With somewhat higher magnification you may be able to see the two chromatids held together by the centromere. As prophase continues , the chromatids continue to thicken and shorten. The nuclear envelope disappears and the beginnings of the spindle apparatus begin to appear.

Prophase

3. At metaphase, the chromosome pairs have moved to the center of the spindle. One particular part of each chromosome, the centromere, attaches to the spindle. The centromeres of all the chromosomes lie about the same level of the spindle called the metaphase plate.

Metaphase

4. At the beginning of anaphase, the centromere regions of each pair of chromatids separate and are moved by the spindle fibers toward opposite poles of the spindle, dragging the rest of the chromatid behind them. Once each chromatid is separate it is called a chromosome.

Anaphase

5. Telophase, the last stage of division, is marked by a pronounced condensation of the chromosomes, followed by the formation of a new nuclear envelope around each group of chromosomes. The chromosomes gradually uncoil into the fine threads of chromatin, and the nucleoli reappears. Cytokinesis may occur. This is the division of the cytoplasm into two new cells. In plants, a new cell wall is laid down between the daughter cells. In animal cells, the old cells will pinch off in the middle along a cleavage furrow to form two new daughter cells.

Telophase

Analysis Questions:
1. Why is it more accurate to call mitosis “nuclear replication” rather than “cellular division”?

_____________________________________________________________________

2. Explain why the whitefish blastula and onion root tip are selected for study of mitosis.

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Exercise 3A.2: Time for Cell Replication
Procedure:
It is hard to imagine that you can estimate how much time a cell spends in each phase of cell replication from a slide of dead cells. Yet this is precisely what you are going to do in this part of the lab. Since you are working with a prepared slide, you cannot get any information about how long it takes a cell to divide. What you can determine is how many cells are in each phase. From this, you can infer the percent of time each cell spends in each phase.

1. Observe every cell in one high power field of view and determine which phase of the cell cycle it is in. This is best done in pairs. The partner observing the slide calls out the phase of each cell while the other partner records. Then switch so the recorder becomes the observer and visa versa. Count at least two full fields of view. If you have not counted 200 cells, then count a third field of view.

2. Record your data in Table 3.1.

Table 3.1

	Number of Cells				Percent of Total Cells Counted	Time in Each Stage
	Field 1	Field 2	Field 3	Total
Interphase
Prophase
Metaphase
Anaphase
Telophase
Total Cells Counted

3. Calculate the percentage of cells in each phase.

Consider it takes, on average, 24 hours (or 1,440 minutes) for onion root-tip cells to complete the cell cycle. You can calculate the amount of time spent in each phase of the cell cycle from the percent of cells in that stage.

Percent of cells in stage X 1,440 minutes = ___________ minutes of cell cycle spent in stage.

Questions:
1. If your observations had not been restricted to the area of the root tip that is actively dividing, how would your results have been different?

_____________________________________________________________________

2. Based on the data in Table 3.1, what can you infer about the relative length of time an onion root-tip cell spends in each stage of cell division?

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Mitosis Activity

Stages of Mitosis

Introduction

Mitosis, also called karyokinesis, is division of the nucleus and its chromosomes. It is followed by division of the cytoplasm known as cytokinesis. Both mitosis and cytokinesis are parts of the life of a cell called the Cell Cycle. Most of the life of a cell is spent in a non-dividing phase called Interphase. Interphase includes G1 stage in which the newly divided cells grow in size, S stage in which the number of chromosomes is doubled and appear as chromatin, and G2 stage where the cell makes the enzymes & other cellular materials needed for mitosis.

Mitosis has 4 major stages — Prophase, Metaphase, Anaphase, and Telophase. When a living organism needs new cells to repair damage, grow, or just maintain its condition, cells undergo mitosis.

During Prophase, the DNA and proteins start to condense. The two centrioles move toward the opposite end of the cell in animals or microtubules are assembled in plants to form a spindle. The nuclear envelope and nucleolus also start to break up.

Prophase

During Metaphase, the spindle apparatus attaches to sister chromatids of each chromosome. All the chromosomes are line up at the equator of the spindle. They are now in their most tightly condensed form.

Metaphase

During Anaphase, the spindle fibers attached to the two sister chromatids of each chromosome contract and separate chromosomes which move to opposite poles of the cell.

Anaphase

In Telophase, as the 2 new cells pinch in half (animal cells) or a cell plate forms (plant cells), the chromosomes become less condensed again and reappear as chromatin. New membrane forms nuclear envelopes and the nucleolus is reformed.

Telophase

Objective:

In this lab, you will determine the approximate time it takes for a cell to pass through each of the four stages of mitosis. You may use your textbook and class notes to help you identify the stages of mitosis as seen under the microscope.

Materials:

Microscope, prepared slide onion root tip or whitefish blastula, textbook, lab worksheet, pencil

Procedure:

Set up a compound light microscope and turn on the light.
Place a slide containing a stained preparation of the Allium (onion root tip) or Whitefish blastula.
Locate the meristematic or growth zone, which is just above the root cap at the very end of the tip or
Focus in on low power, and then switch to medium or high power. Below find micrographs of the four stages of mitosis. Use them to help you identify the stages on the microscope slide.

Prophase (onion)

Metaphase (onion)

Anaphase (onion)

Telophase (whitefish)

Now count the number of cells found in each stage of mitosis and place the data in the chart below.
Determine the percentage of time each cell will spend in each stage of mitosis. Divide the number of each cell by the total number of cells and multiply by 100 to determine the percentage. Place these values in the chart below.

Stage of Mitosis	Number of Cells	Percent of time in each stage = # of cells in stage X 100% Total # of Cell
Prophase		%
Metaphase		%
Anaphase		%
Telophase		%
Interphase (Not a Mitotic Stage)		%
Total # cells		100%

Line graph the data you have just collected. Be sure to label the X and Y axis & include the units of measurement.

Title: __________________________________________________

Graph Legend:

Questions:

1. Of the four stages of mitosis, which one takes the most time to complete?

2. Which is the shortest stage in duration?

3. What would happen if the process of mitosis skipped metaphase? telophase?

Further Study:

Normal Cell Division may be observed in onion root tips. Many of the processes are similar to those in animal cells. However, in plant cells, the cell plate between daughter cells forms from the Golgi.

Find all of the stages of mitosis and interphase in the above picture. Make a sketch of each stage and briefly describe what is occurring. Count and record the number of cells you see in each stage.

	Projects
	Notes

Meiosis Labeling

Meiosis

On each of the images, label the phase of meiosis

1. _______________	2. _______________	3. _______________
4. _______________	5. _______________	6. _______________
7. _______________	8._______________	9._______________
10. _______________	11. A cell with a diploid number of 20 undergoes meiosis. This will produce ________ daughter cells, each with ________ chromosomes. 12. Synapsis occurs during this phase: _______________________ 13 How many different possible combinations are there for a cell that has 10 chromosomes (5 pairs): _____________ 14. Tetrads line up along the equator during this phase: ______________ 15. At the end of meiosis I, ________ daughter cells are created. These daughter cells are [ diploid \| haploid ]. 16. Meiosis occurs in what type of cells: ____________________________

Now label the photographs.
17. _______________	18. _______________	19. _____________
20. _______________	21. _______________	22. _____________
23. _______________	24. _______________	24. _____________
25. _______________

McMush Lab

McMush

Introduction:
Carbohydrates, proteins, fats, vitamins, and other nutrients provide your body with energy necessary to carry on life activities. These compounds are present in the plants and animals you use as food. In this lab, you will test for specific compounds and then determine if those compounds are present in ordinary foods.

Objective:
To determine the compounds present in food.

Materials
McDonald’s Happy Meal (fries + drink included) (no toy!), beaker, graduated cylinder, test tubes, test tube clamp, hot plate, Benedict’s solution, Biuret solution, Indophenol (DPIP) solution, Lugol’s iodine solution, 1% silver nitrate solution, blender

Procedure:
Part I – Testing of Known Substances

Protein test:

Place 5 ml of the gelatin solution into your test tube.
Add ten drops of Biuret solution.
Observe any color change

Glucose test:

Place 5 ml of the glucose solution into your test tube.
Add 3 ml of Benedict’s solution.
Place the tube in a beaker of boiling water and boil for five minutes
Use test tube clamps to hold hot test tubes.
Observe any color change

Starch test:

Place 5 ml of the starch solution into your test tube.
Add 5 drops of Lugol’s iodine solution.
Observe any color change

Vitamin C test:

Place 5 ml of the vitamin C solution into your test tube.
Add 5 drops of indophenol solution.
Observe any color change

Chloride test:

Place 5 ml of the salt solution into your test tube.
Add 5 drops of silver nitrate solution.
Observe any color change.

Record your results in a data table:

Food Substance	Reagent test	Results
Gelatin	Biuret solution
Glucose	Benedict’s solution
Starch	Lugol’s iodine solution
Vitamin C	indophenol solution
Sodium chloride	silver nitrate solution

Procedure:
Part II – Testing McMush

Place the Happy in a blender. Add enough water to cover and blend until you get an emulsion.
Filter the mush in to a beaker.
Predict the substances you will find in the McMush solution. Record your predictions in the data table using a “ +” or “-“.
Repeat the reagent tests above using 5 ml of the McMush solution.
Describe and record your results.

Food Substance	Prediction	Reagent test	Results
Protein		Biuret Solution
Sugar		Benedict’s Solution
Starch		Lugol’s solution
Vitamin C		Indophenol Solution
Sodium Chloride		Silver Nitrate Solution

Adapted from a lab by C. Sheldon

Matter Outline

MATTER

PHYSICAL PROPERTIES

Everything is made up of matter.
The formal definition is anything that has mass and takes up space
Can be measured or observed

c. Match the property to the definition below:

Mass the concentration of matter in an object

Weight the amount of matter in an object

Volume measure of the pull of gravity on an object

Density the amount of space an object takes up

II. Mixtures and Solutions

a. A bowl of cereal and milk is an example of a mixture. That’s a combination of two or more different kinds of matter, each of which keeps its own physical properties.

b. In a solution the particles of two or more substances are evenly distributed.

c. When a substance can be dissolved in another substance (like sugar in water) we call this solubility.

III. Changes in State

a. The three stages of matter are solid, liquid and gas.

b. Draw the arrangement of the particles in each state of matter and describe the speed of their movement as well as how close together they are using the diagram below.

gas, moving very fast,

& really far apart

liquid, faster moving,

& spread apart

Solid, slow moving,

& close together

c. When heat is added to a substance, the particles vibrate faster and move apart.

d. When heat is removed from a substance, the particles vibrate slower and move closer.

IV. Physical and Chemical Changes

a. When a physical change occurs the matter may look different, but

it doesn’t change.

b. When a chemical change occurs a new substance may form.

c. List three ways to know that a chemical change may have occurred.

gas produced, light, and heat.

d. Draw circles around chemical changes & underline physical changes below:

i. cutting a piece of paper into small pieces

ii. boiling water

iii. a nail rusting

iv. freezing water

e. The chemical property of combustibility describes substances that result in flame or burning.

f. The ability of a substance to react chemically is reactivity.

V. Conservation of Matter

a. Matter cannot be created nor destroyed.

b. In class we dissolved Alka Seltzer in a bottle of water. A gas was produced. We caught the gas in a balloon. Though a new substance was formed (the gas) the total mass didn’t change.

VI. Atoms and Electrons

a. The atomic number refers to the number of protons in the nucleus of an atom. The number ofprotons also determines what kind of element an atom is.

b. The element oxygen has 8 protons in its nucleus. All atoms that have 8 protons in the nucleus are oxygen atoms.

c. Be able to label the diagram of an atom. (see notes)

VII. Metals

a. Match the property to its definition by drawing a line:

Malleable electricity and heat travel easily through metals

Ductile shiny

Conductor used as a wire

Luster able to be hammered or rolled

VIII. Compounds and the Periodic Table

a. A compound is different from an element because a compound has more than one type of element in it.

b. The Periodic Table has elements arranged in order of increasing atomic number.