Biology
Mitosis and Meiosis

Mitosis & Meiosis

Standards

SB1. Students will analyze the nature of the relationships between structures and functions in living cells.

SB2. Students will analyze how biological traits are passed on to successive generations.


Learning Tasks



Overview

In this unit, you will explore the reasons why most cells must reproduce. You will learn about the cell cycle and the stages of mitosis. After distinguishing between haploid and diploid cells, students will see the logic behind the process of meiosis. You will predict what will happen as mitosis and meiosis occurs. You will analyze the differences between the two processes and evaluate the efficacy of asexual and sexual reproduction in light of an ever changing environment. You will study and compare the stages of meiosis in males and females. Finally, you will realize that due to its ability to allow for genetic recombination, meiosis not only results in genetic continuity, but also, along with fertilization, leads to genetic diversity.

 


Key Terms

Click here to download a list of key terms for this module. 

 

 


Pre-Assessment: Mitosis and Meiosis Quiz

 

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Please click on the Quizzes tab on the navigation bar in your Course Home page and take the Pre-Assessment Mitosis and Meiosis Quiz. You will have a limited amount of time to complete the test. You will not receive a grade for this assessment but it will give your instructor an indication of what your already know and what you still need to know.


Introduction to Cell Division: Recorded Lecture Notes

 

The following video accompanies the notes that will be provided in this module.

Screenshot of and link to notes about cell division

 


  

Notes: Mitosis

 

Cell Growth and Reproduction

 

Living things usually grow by producing more cells, rather than increasing the size of the cell. In the tissue below, several stages of cell division can be seen.

Image of mitosis

Image source

Cells cannot get very big. Large size causes several problems for cells. The limitations of exchanging materials include the following.

  1. Cells need to take in food, water and oxygen, and this occurs through the cell membrane.

  2. Cells also produce waste products, including carbon dioxide, which leave the cell through the cell membrane.

  3. However, the larger a cell becomes, the faster nutrients are required and wastes are produced.

  4. Also, as a cell increases in size by just a small amount, its surface area to volume ratio actually decreases by a significant amount. Therefore, even though the demands for nutrient and waste exchange are increased, the amount of surface area on the cell membrane where these exchanges could occur is actually decreased!  A traffic jam would quickly occur in the cell!

Examine the 4 templates below. If you were to cut out the templates, you could fold each one into a cube. You could also measure and compare the ratio of each cube's surface area to its volume. If you did so, you would find that the surface area to volume ratio on the smallest cube is relatively large, meaning that there is a lot of surface area in relation to the volume of that cube. A one inch square box has a surface to volume ratio of 6mm2 : 1mm3.

Image showing 3 unit cube models  

On the other hand, you would find a much smaller difference in the surface area to volume ratio in the largest cube. A four inch cube has a surface to volume ratio of 24mm2 : 8cm3. (24:8 could be considered 3:1 for the large cube compared to 6:1 for the smaller cube.)

That means that the volume of a large cell has relatively little surface area to service it. If these cubes were cells, the large one would not have enough surface area to provide nutrients and get rid of wastes. That is why cells do not grow into gigantic blobs.

To actually calculate the ratio of surface area to volume, follow the following set of instructions:

volume = side 1 x side 2 x side 3 (cubic centimeters)

surface area = 6 x side 1 x side 2 (square centimeters).

The ratio of surface area to volume equals ratio = surface area/ volume

Cell Division - the process of creating two new cells occurs in two steps: 

Just before each cell divides, the cell replicates, or copies, all of its DNA so that each new daughter cell gets a complete set of genetic information; then the nucleus itself divides into two new nuclei; this is called Mitosis.

When the nucleus has completed its division the rest of the cell divides to form two new daughter cells through a process called cytokinesis.

Chromosomes, the Cell Cycle, and Mitosis

Remember DNA is a nucleic acid and one of the 4 types of macromolecules within cells.

DNA is composed of monomer units called nucleotides.

When a eukaryotic cell is not reproducing, its DNA is inside the nucleus as disorganized, long strands called chromatin.

Before a cell divides, the chromatin thickens and shortens into distinctly visible bodies called chromosomes, like the metaphase chromosomes shown below.

Image of chromosome--enlarged

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Each chromosome is a single DNA molecule. It is associated with proteins called histone proteins. 

In order for a cell to divide, its chromosomes must first make a copy of themselves (in a process called chromosome replication) so that each new daughter cell gets the original amount of chromosomes.

Just before chromosome replication occurs, each chromosome shortens.

Just after chromosome replication occurs, the two chromosomes (old one and new one) are stuck together. These 2 structures are referred to as sister chromatids.  They are joined together by a central protein bundle called the centromere.  The sister chromatids are exact copies of each other, and each one will be distributed to one of the new daughter cells.

Chromosomes with centromere and chromatids identified

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Each species has a characteristic number of chromosomes in the nucleus of all of its cells. The number of chromosomes has nothing to do with the complexity of the organism.

The human chromosome number is 46.

Below is a picture, called a karyotype, of each of the 46 human replicated chromosomes.  (This particular karyotype is not a normal one; it shows a mutated condition called trisomy 21 meaning that there are 3 of the 21st chromosome)

 

 

Karyotype showing trisomy  

Image source 

The human chromosomes include  2 sex chromosomes, X and Y, which determine the sex of the individual.  A sex chromosome combination of XY is a male and XX is a female.  The other 44 chromosomes are called autosomes, and they carry genes for all of the other traits of an individual. 

Also notice that the 46 human chromosomes are arranged in 23 pairs so that there are two of each type of chromosome.  These are called homologous pairs and each chromosome of the pair is called a homolog

Each homolog carries genes for a particular trait in the same place on its own chromosome. For this reason, every individual has two alternate forms of each gene that are referred to as alleles.  Half of an individuals genetic information comes from the mother and the other half comes from the father.

All of the body cells, referred to as somatic cells of a human (ex:  skin cells, liver cells, bone cells, nerve cells, etc.) have 46 chromosomes in them.  They have all 23 homologous pairs consisting of 46 homologs. 

Only the sex cells, called gametes (sperm and egg), of a human do not have all 46 chromosomes.  These cells have half of the total chromosome number, in this case, 23.  Gametes have one homolog of each chromosome pair in the nucleus of its cells. When a sperm and egg unite in fertilization, the total number of chromosomes is restored to 46. 

When a body cell of an organism has the full amount of chromosomes, with all of its homologous pairs, such as a human cell containing 46 chromosomes, it is said to have the diploid number of chromosomes.  This is because di- means two and these cells have two of each type of chromosome present.  The human diploid number, then, is 46.

When a gamete of an organism has half of the full amount of chromosomes, such as a human sperm cell containing 23 chromosomes, it is said to have the haploid number of chromosomes.  Just think of haploid-half.  The human haploid number, then, is 23. 

So how is it that certain cells of the body end up with the diploid number of chromosomes (the full amount) and other body cells, specifically the sex cells, end up with the haploid number of chromosomes (half of the full amount)?

The answer is that the body cells (skin, nerve, liver, bone, etc.) are produced by a type of cell division that begins with mitosis. 

 

Image of process of mitosis

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The end result of mitosis, followed by cytokinesis, is two identical diploid somatic cells. Gametes (egg and sperm) are produced in the ovaries and testes. They are produced by a type of cell division called meiosis.  The end result of meiosis is the production of 4 haploid gametes.  

 


 

Notes: Mitosis (Continued)

The purpose of mitosis is to allow an organism's body cells to divide into genetically identical body cells of the same type while maintaining the same chromosome number.  In other words, a skin cell needs to divide into two daughter skin cells that are genetically the same as the parent cell and still have 46 chromosomes.  Mitosis is characterized by a diploid cell dividing into two daughter cells that are also both diploid. 

The purpose of meiosis is for cells inside the ovaries and testes to divide into genetically different sex cells while cutting the chromosome number in half.  Therefore, sperm and egg will have half of the correct amount of chromosomes so that when they meet each other in a process called fertilization, the first cell of the embryo, called a zygote, will have the correct full amount of chromosomes.  Meiosis is characterized by a special diploid cell inside the ovaries or testes dividing into four haploid daughter gamete cells.

Both types of cell division, mitosis and meiosis, are just a part of the entire life cycle of the parent cell called the cell cycle.

Cell cycle - the series of events that a cell goes through as it grows, prepares for cell division, and divides to form daughter cells, each of which then begins the cycle again.

 

 

Image of eukaryotic cell cycle

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 The cell cycle consists of four phases:  G1, S, G2 and M phases.

The first three phases, G1, S, and G2, are combined and collectively known as interphase. 

During interphase the chromosomes are disorganized and present as chromatin. If you look at an interphase cell under the microscope, you cannot distinguish separate chromosomes. During interphase, the cell is carrying out its normal everyday cell activities as well as preparing for the M phase.

G1 phase the first part of interphase where the cell grows and produces more proteins and organelles.

S phase the second part of interphase where DNA is replicated (here, the chromosomes go from single form to doubled form).

G2 phase final part of interphase where the cell produces many of the organelles and molecules required for the M phase.

M phase - the beginning of the actual cell division process, either mitosis for body cells that are dividing, or meiosis for the formation of gametes.  Mitosis and meiosis are actually the division of the nucleus of cells, so that each daughter cell gets the correct diploid or haploid number of chromosomes.  The end of the M phase is marked by a process called cytokinesis, the division of the cytoplasm which surrounds the nucleus.

When a body cell enters mitosis, its goal is to separate the now doubled chromosomes (which occurred in the S phase) so that each of its two daughter cells has the diploid number of genetically identical chromosomes. Mitosis consists of four phases. You'll see images of the four phases below (originally from University of North Carolina Charotte). These images will help you identify the four phases of mitosis.

Prophase the first phase of mitosis characterized by a disappearance of the nuclear membrane and nucleolus.  The already replicated chromosomes are now clearly visible. Microtubules within the cell gather together to form a spindle, or basket-like framework. The picture below is of a cell in prophase.

 

Image of prophase

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Metaphase the second phase of mitosis where all of the doubled chromosomes, now attached to the individual fibers of the spindle basket, move to the center of the cell, called the equator.

Image of metaphase

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Anaphase the third phase of mitosis where the spindle fibers shorten from the poles, pulling the doubled chromosomes apart from each other, toward the poles of the cell.

anaphase.png
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Telophase the final phase of mitosis characterized by the separated chromosomes reaching the poles of the cell.  The nuclear membrane and nucleolus begins to reappear around each set of chromosomes. 

Image of telophase  

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The end of telophase is marked by cytokinesis, or the division of the cytoplasm.  In animal cells, cytokinesis occurs as the cell membrane pinches inward until the two daughter cells pop apart.

Image of mitosis in an animal cell

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Closely examine the process of mitosis in a plant cell in the following diagram:

Image of mitosis in plant cells

There are two important differences between cell division in animal cells and plant cells. 

In plant cells, cytokinesis occurs as a cell plate (which eventually forms a cell wall) begins to grow out from the center and merely separates the two daughter cells. Plant cells do not have centrioles that form the visible microtubules that form the spindle basket; there is a mysterious structure called the microtubule organizing center which performs the job of the centriole.

Image of cell plate forming in an onion cell

 

Examine the pictures below of mitosis in plant cells, and find all stages, including cytokinesis.

  

 

After mitosis, two new daughter cells, each with a diploid number (full set) of chromosomes, are formed.  The two daughter cells are genetically identical to each other.  They still end up with the diploid number of chromosomes. 

Image of onion cells undergoing mitosis

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Meiosis will be detailed in Notes: Meiosis

 


 

BrainPOP Video and Lab Activity

 

For a better understanding of Mitosis, view the following BrainPOP video on the subject. Before watching the video and taking the quiz, read and think about the questions.

 

Screenshot of and link to BrainPop video about Mitosis

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After viewing the movie, go to QUIZZES and choose the quiz titled Mitosis BrainPOP Quiz.

After completing the quiz, go to the BrainPOP Mitosis experiment and complete a simple (yet odiferous) at-home lab.

 

Image of lab rat investigating onions and link to BrainPop experiment

 Follow the instructions for this lab activity. 

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Have someone assist your with slicing the onion.  Be very careful with sharp instruments. The thin film of tissue between the layers of the onion is the onion part that you should use.  If you have access to a microscope, place the onion tissue on a slide with a coverslip over the onion skin.

 


 

Cell Division Step-By-Step Interactive

Here's an interactive presentation about cell division from Teacher's Domain. Adapted from a resource created by the Exploratorium, this presentation takes you through a process that is critical to life—cell division. As you recall, division enables cells to replicate their genetic material and then create an exact copy of themselves. Watch the presentation and explore the individual steps of this process, by which single-celled organisms reproduce and multicellular organisms develop, grow, repair damaged tissue, and reproduce. Simply read the information and click on arrows to see mitosis as it occurs.

 


Mitosis:  Online!

Go to The Cell Cycle & Mitosis Tutorial: DNA Basics page. Read the information about DNA Basics.

Scfeenshot of and link to Cell Cycle and Mitosis Tutorial: DNA Basics

 

Afterward, continue to click on NEXT and read each section of the Cell Cycle & Mitosis Tutorial.

Screenshot and link to page 2 of The Cell Cycle & Mitosis Tutorial: The Cell Cycle .Page 3 of The Cell Cycle and Mitosis Tutorial

 

Watch the Mitosis Animation video or Flash presentation.

Screenshot of and link to page of mitosis animation

 

Afterward, click NEXT and answer all eleven of the Tutorial Questions.

Screenshot of and link to online tutorial questions about mitosis

 

Go to Online Onion Root Tips: Phases of the Cell Cycle page. Read and follow instructions, (clicking on NEXT at bottom of each page) until you complete the lab.

Screenshot of and link to Online Root Tips website .Screenshot and link to web page about time spent in phases of cell cycle

 

 

Complete the table shown on the page below as you go. If you want or need a copy of the table, click here to download a copy.

stepScreen shot of and link to online table completion activity08.png

 

This is the type of information you are being asked to supply:

Image of and link to data table for activity.

 

Calculate the % of time spent in each phase. If you need help, remember this: the % of cells in any phase equals number of cells in phase divided by total number of cells. To find the amount of time, simply multiply the % cells in phases by 24 hours.

 


 

Breast Cancer Discussion

Read the article about breast cancer titled BRCA1 and BRCA2: Cancer Risk and Genetic Testing.

Logo of and link to the National Cancer Institute

 

Discussion icon

After reading the article, answer the questions below in the Breast Cancer Discussion. You must respond to at least two other people in your class.

  1. What are the advantages to undergoing genetic testing for breast cancer?
  2. What are the disadvantages to undergoing genetic testing for breast cancer?
  3. In your opinion, what group of women would receive the most benefit from genetic testing for breast cancer?

 


 

Mitosis Timeline Investigation

In this activity, you will examine a photograph of cells from the actively growing tip of an onion root. You will examine each cell and determine what phase it is in. At the end you will count up the cells found in each phase and use those numbers to predict how much time a dividing cell spends in each phase.

Here are photographs to help you train your eyes on different phases. 

  

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Now, look at the photograph below. If you need a bigger image to examine, just click on the photograph. Another window will open, containing a larger image.

Image of onion cells undergoing various stages of mitosis

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Enter your data in the table below.

Image of and link to word processing document of a data table

 

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Click here to download a hardcopy/offline version of the table. Recall from the Online Mitosis Lab: the % cells in any phase equals number of cells in phase divided by total number of cells. To find amount of time, simply multiply the % cells in phases by 24 hours.

*There are approximately 61 cells visible in the final photograph. Some of the empty cells do not have a nucleus visible and are not included in the count.

Next, answer the following questions.

  1. What phase are most cells found in?
  2. What type of cells undergo mitosis?
  3. What happens during metaphase?
  4. What is the purpose of the spindle fibers?
  5. What is happening during interphase?
  6. Explain how the process of mitosis helps an organism to grow in size.

 

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When you have completed your work submit it to the dropbox titled Mitosis Time Investigation.

 


 

Mitosis and Cytokinesis Study Guide

 

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Download a copy of questions below.

Use your notes and the resources provided to answer the questions. Keep a copy of your work in your notebook.

Chromosomes
1. Is the following sentence true or false? Chromosomes are not visible in most cells except during cell division.

Image of chromosome

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Genetics Home Reference's informative What is a Chromosme? page has some information that'll help you get the answer.

2. When chromosomes do become visible at the beginning of cell division, what does each chromosome consist of?
Dr. Pavan of the National Human Genome Research Institute might be able to shed some light on this question.

Dr. Pavan of the National Human Genome Research Institute

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3. Each pair of chromatids is attached at an area called the ____.

Cartoon genyleman points out the answer to the question is image 1

4. The period of growth in between cell divisions is called ___.

5. What is the cell cycle?

Image of animal with a motor cycle

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6. Write the names of each of the four phases of the cell cycle.

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7. The division of the cell nucleus during the M phase of the cell cycle is called ____.

Events of the Cell Cycle

8. Interphase is divided into what three phases?

9. What happens during the G1 phase? Answer!

10. What happens during the S phase? Answer!

Cartoon gentleman standing in DNA spiral suggests that the S-Phase may have something to do with DNA

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11. What happens during the G2 phase? Answer!

 Mitosis

12. What are the four phases of mitosis? Answer!

*Just in case you're interested, some folks refer to 6 phases of mitosis by by including the other two parts of the cell's life span, interphase and cytokinesis.

13. Which of the choices below is the of the name for the two tiny structures located in the cytoplasm near the nuclear envelope at the beginning of prophase? _____

Cartoon gentelman obviously pointing to centrioles

a. centrioles

b. spindles      

c. centromeres

d. chromatids

 

14. What is the spindle?

Questions 15 through 20

Match the description of the event with the phase of mitosis it is in. Each phase may be used more than once. The phases are:

A. Prophase

B. Metaphase

C. Anaphase

D. Telophase

 

15. _____ The chromosomes move until they form two groups near the poles of the spindle

16. _____ The chromosomes become visible

17. _____ A nuclear envelope re-forms around each cluster of  chromosomes 

18. _____ The centrioles take up positions on opposite sides of the nucleus.

19. _____ The chromosomes line up across the center of the cell.

20. _____ The nucleolus becomes visible in each daughter nucleus.

 

Cytokinesis

21. What is cytokinesis? division of the cytoplasm

22. How does cytokinesis occur in most animal cells?

23. Which of the choices below forms midway between the divided nucleus during cytokinesis in plant cells?

a. cell nucleus

b. cytoplasm

c. cell plate

d. cytoplasmic organelles

 


Mitosis and Cytokinesis Assignment Check

 

You should have your Mitosis and Cytokinesis Study Guide completed and with you as you complete the following assignment check.

 

Quiz icon
Go to the navigation bar and click on QUIZZES. Choose the quiz entitled Mitosis and Cytokinesis AC.

 


 

Meiosis Notes

1. Meiosis: cell division that results in haploid gametes; used for sexual reproduction: sperm and egg each carry one set of genetic information; when combined, a new "genome" is created so that all offspring carry traits of both parents;  occurs in the same four phases as mitosis with the following differences:

A. Occurs with two "sessions" of divisions continuously but with no replications of chromosomes between Meiosis I and Meiosis II 

1. Homologous Chromosomes: chromosomes that contain different "versions" of genes for the same traits; one came from mother, its matching homolog came from the father; therefore, there are two of each kind of chromosome in every body cell (for example, one kind of chromosome carries the gene for blue eyes but its homolog may carry the gene for brown eyes so they are the same kind of chromosome, i.e., homologs)

2. Diploid Cells: have two of every kind of chromosome, one set that came from each parent; females received an X chromsome from both parents so are XX; males receive an X chromosome from the mother and a Y chromosome from the father so males are XY.

3.  Haploid Cells: have one of each kind chromosome; also known as sex cells or gametes; male and female gametes must fuse (fertilization) to form a diploid zygote that will undergo mitosis to develop into an organism

Image of the Meiosis process

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B. In Meiosis I:  all chromosomes make copies of themselves.  This doubles the number of chromosomes in the cell; while each chromosome is still attached to its copy, each is referred to as a chromatid.

Single and double strand chromosomes

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1. Prophase I, homologous chromosomes from each parent pair up to form two attached sets of chromtids called a tetrad;  there are many variations in the way that they line up; this is one source of genetic variation 

2. In Metaphase I, each tetrad lines up and attaches to a single spindle fiber; crossing over of chromosomes may occur to provide additional genetic variation among offspring; each chromatid may exchange a part of itself with its homolog; this is a second source for genetic variation

genetic material crossing over

 

Genetic variation--chromosomes splitting

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You can see here that the cell began with four chromosomes, two of each kind; after meiosis II there are only two chromosomes, one of each kind.

3. In Anaphase I, tetrads are separated so that sister chromatids are still attached to their duplicates; its homolog will go to the other cell; the cell to which each goes is totally random and leads to the Law of Independent Assortment: each set of tetrads separates independently of any other set.  

4. In Telophase 1, cells may finish cytokenesis or proceed immediately with meiosis II 

C. In Meiosis II: (begins in same two cells just created; this part occurs in a manner very similar to mitosis) 

1. Prophase II, chromosomes did not replicate; this means that each cell has only one of each kind of chromosome along with its exact duplicate;  at this point, the cell is haploid because it no longer has one of every kind of chromosome that was in the original cell. 

2. Metaphase II, sister chromatids line up on individual spindle fibers 

3. Anaphase II, sister chromatids are separated into each new cell so that each cell now has only half as many chromosomes as the original cell in Prophase I (one of each kind); this process illustrates the Law of Segregation: chromosomes will be separated in such a way that every cell receives one of each kind of chromosome. 

4. Telophase II, each of the four cells completes reforming nuclei and cytokenesis separates the four new haploid cells

2. Genetic recombinations (variations) can come from crossing over, random arrangement of tetrads, and random combinations of sperm and eggs. 

3. Oogenesis: meiosis that produces eggs (ova); one viable, and three tiny polar bodies, all with correct # of chromosomes but only one ovum large enough to survive and be fertilized; the polar bodies will dissolve

Oogenesis

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Oogenesis, shown on the left, leaves one gamete with most of the cytoplasm.  Spermatogenesis creates four sperm of equal size. 

4. Spermatogenesis: meiosis that produces sperm; all four are tiny and all four are capable of fertilizing an egg (ova); process is similar to oogenesis 

5. Nondisjunction Mutations: improper separation of sister chromatids may result in a cell having one too many chromosomes (trisomy) or not having one of a certain chromosome (momosomy);

A. Trisomy 21, Down Syndrome 

B. Trisomy 23, Klinefelter Syndrome: XXY

C. Monosomy 23, Turner Syndrome: XO 

6.  Karyotype: a picture of an individual's chromosomes so that the above types of mutations might be seen; a fetus's cells may be collected by:

A. Amniocentesis: long needle withdraws fluid around fetus; some of the embryo's cells that have sloughed off into the fluid will be collected and examined

B. Chorionic Villi Testing: scraping a few cells from villi of the placenta which connect fetus to mother in the uterus 

7.  Ultrasound pictures can be taken in uterus to determine gross structural abnormalities; this is a safe and non-invasive procedure 

8.  Advantages and disadvantages of sexual reproduction compared to asexual reproduction:

Difference between sexual and asexual reproduction

 

Sexually repoducing organisms

Asexually reproducing organisms

Number of offspring

Usually limited to small sets, 1 to 10 at a time, but can be hundreds ib the case of some arthropods

Generally only one new organism per division

Number of parents required to reproduce

At least 2; some species will not reproduce if the population is small

Only one, since it simply divides itself

Genetic variation

Yes, through crossing over, independent assortment of chromosomes and recombination of genomes

None; each offspring is an exact copy of its parent

Gestation or care of young

Yes, some internally reproducing organisms have protective structures for embryos and may care for their young

None; no responsibility for parent

Adaptability to changing environmental conditions

Good since traits are randomly shuffled and passed on to offspring

Poor since the only opportunity for variation comes from mutations

Lifespan

Lifespan can be very short or hundreds of years; reproductive

Lifespan is usually short since each generation "disappears" with each division

Reproductive Season

Limited; can depend upon age of individuals or specific times of fertility

Unlimited; can reproduce as frequently as every 30 minutes, indefinitely

Any organism that can produce gametes, sperm & egg, pollen or spores is considered to be a sexually reproducing organism.  Those who can reproduce by dividing, budding or fragmentation are considered asexual.  A few species can do both, depending on the circumstances.

Considering the above information, if you could choose how the human race should reproduce to be most successful, which would you select?  Why?

 


 

Meiosis Online Tutorial

 

Go to the University of Arizona's Biology Project Meiosis Tutorial website.

Screenshot of and link to the University of Arizona Meiosis Tutorial Website.

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Visit the the Reproduction portion of the site and read all of the material on each page.

Afterward, view the Meiosis I and Meiosis II animations. It's a good idea to view these several times! Continue by clicking next, reading all information until you reach the Test Yourself page.  Answer each question.  If you select an incorrect response, be sure to read the information the tutorial provides. This will be an excellent review for quizzes and tests on this topic.

 


Meiosis and Diversity

The DragonMeiosis site below gives you an opportunity to select 'dragon' gametes and attempt to create an offspring with the traits of your choice. In doing so, you will learn more about meiosis.

dragon-screen.jpg Image source

 


 

Meiosis Practice Activity

Used what you have learned up until this point in the course to answer the following questions.  You may download a copy of the questions if you want to use them offline. Have your answered questions with you when you complete the assignment check for meiosis.

 

Meiosis  - Chromosome Number

1. What does it mean when two sets of chromosomes are homologous? Answer!

___ 2. Write the letter or letters that describe a diploid cell in the blank to the left.

a. 2N

b. Contains two sets of homologous chromosomes

c. Contains a single set of homologous chromosomes

d. A gamete 

___3 If a Drosophila cell has a diploid number of 8, what is its haploid number?

a. 8

b. 4

c. 2

d. 0

Phases of Meiosis

4. Why is meiosis described as a process of reduction division? 

5. What are the two distinct stages of meiosis? 

6. Is the following sentence true or false? The diploid cell that enters meiosis becomes 4 haploid cells at the end of meiosis. Answer! 

7. How does a tetrad form in prophase I of meiosis?

___ 8. Write the number of chromatids in a tetrad in the blank to the left.

a. 8

b. 6

c. 4

d. 2

 9. What is the result of the process of crossing-over during prophase I? 

___  10. Write the letter of each sentence that is TRUE about meiosis in the blank to the left.

a. During meiosis I, homologous chromosomes separate.

b. The two daughter cells produced by meiosis I still have the two complete sets of chromosomes as a diploid cell does.

c. During anaphase II, the paired chromatids separate.

d. After meiosis II, the four daughter cells contain the diploid number of chromosomes. 

 

Gamete Formation

11. Match the products of meiosis with the descriptions.

 Toggle open/close quiz question 

Comparing Mitosis and Meiosis
___12.
Write the letter of each sentence that is true about mitosis and meiosis in the blank to the left.

a. Mitosis produces four genetically different haploid cells.

b. Meiosis produces two genetically identical diploid cells.

c. Mitosis begins with a diploid cell.

d. Meiosis begins with a diploid cell.

 

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When you have completed this activity, proceed to QUIZZES and choose the quiz titled Meiosis Practice Activity AC.


Mitosis & Meiosis Interactive Practice

Visit Biology in Motion's interactive Mitosis and Meiosis interactive practice site. Note the difference between these two cellular processes. Practice predicting the steps of mitosis and meiosis. This is a great way to review for quizzes and tests!

Screenshot of and link to Biology in Motion: Mitosis and Meiosis interactive practice site

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Mitosis vs Meiosis Interactive Activity: Comparing Mitosis and Meiosis

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Visit the PBS program NOVA's useful How Cells Divide site. Carefully read each window before advancing to the next.  The information you see will help you complete the activity below. If you pay close attention to each scene, you will see the events of mitosis and meiosis compared side by side.  Make a list of all the differences that you notice and another list of all the similarities. Download the mitosis and meiosis document. Use what you learn to determine whether the following characteristics apply to mitosis, meiosis or both.

 

pbs-mitosis-meiosis-comparison.png

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Submit your completed work to the dropbox titled Mitosis vs Meiosis.

 


 

Interactive Presentation: How Cancer Grows and Metastasizes

Go to the NOVA Online: How Cancer Grows webpage shown below.

Screenshot of and link to PBS Nova interactive presentation about how cancer metastisizes

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Once there, view the flash video showing how a cancer develops and metastasizes.  Be prepared to answer questions about cancer cells and metastasis on upcoming quizzes or tests.

 


 

 

Mitosis & Meiosis Understanding Check

 

Answer the following questions. It's a good opportunity to review what you think you know about this module.

4 phases of mitosis

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Image of process of mitosis

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Image of cells in different phases of mitosis

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Image of daughter cells

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Image of chromosomes

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Sister chromatids cartoon--image shows 2 sister chromatids

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image showing how haploid cells are created

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sequence for mitosis

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Which of the following characteristics in the table below apply to mitosis, meiosis or both?

 

 Click here for a completed version of the table.


Sexual vs Asexual Reproduction

Classic image of Alice talking with the Red Queen Image source

"Well, in our country," said Alice, still panting a little, "you'd generally get to somewhere else — if you run very fast for a long time, as we've been doing."

"A slow sort of country!" said the Queen. "Now, here, you see, it takes all the running you can do, to keep in the same place. If you want to get somewhere else, you must run at least twice as fast as that!"

Taken from Lewis Carroll's classic tale Through the Looking-Glass.

As you watch the short PBS video below, listen very carefully for disadvantages and advantages of sexual and asexual reproduction. Write down several of them.  Also listen for an explanation of the Red Queen Hypothesis.

Asexualandsexualreproduction

Video source

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Next, discuss briefly what is meant by the Red Queen Hypothesis and whether or not you think this is a hypothesis that is supported by the data presented by the scientists in the video. You may want to refer back to the last section of your notes on Meiosis before completing your answers.

 

Post your response to the DISCUSSION titled Sexual vs Asexual Reproduction.

  



Assignments

Before continuing on to the Unit Test, be sure the following graded items have been completed. Click on a link below to return to the page in the module containing the assignment.

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Mitosis BrainPOP Quiz

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Breast Cancer Discussion

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Mitosis Time Investigation (counts as lab)

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Mitosis and Cytokinesis AC

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Meiosis Practice Activity AC

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Mitosis vs Meiosis (counts as lab)

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Sexual vs Asexual Reproduction

 

 


Mitosis and Meiosis Unit Test

 

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Go to the navigation bar and click on QUIZZES. Choose the selection titled Mitosis and Meiosis Unit Test.