mitomeio

Objectives Unit Two: Mitosis, Meiosis and the Cell Cycle

1. Define the following terms and utilize these terms in an appropriate context:
Cell Cycle                      centriole                       centromere                      chiasma
chromatid                       chromatin                     crossing over                   cytokinesis
diploid                           genome                         karyotype                        nonsister chromatids
polytene chromosome                                         lampbrush chromosome
synapsis                          tetrad                           zygote                             cloning

2. Describe the role the following cellular components play in the storage, expression, or transmission of genetic information: A. chromatin B. nucleolus, C. ribosime D. mitochondria E. centriole F. centromere.

3. Discuss the concept of homologous chromosomes, diploidy and haploidy.

4. Describe the characteristics that are shared between two chromosomes considered to be homologous.

5. Describe the differences between two non-homologous chromosomes even if they are from the same species, have the same length and have similar centromere placements.

6. Classify chromosomes as metacentric, submetacentric, acrocentric or telocentric based upon centromere location. Identify the "p arm" and the "q arm" of a chromosome.

7. Given an organisms diploid number, determine how many chromatids are visible at the end of mitotic prophase.

8. Given an organisms diploid number, determine how many chromosomes would be viewed moving to each pole during anaphase of mitosis.

9. Outline and discuss the events of the cell cycle.

10. Describe the events that characterize each stage of mitosis.

11. Contrast telophase in plant and animal mitosis.

12. Ignoring the details of spindle formation, nuclear membrane changes etc., diagram mitosis in a cell with any given number of chromosomes.

13. Contrast the end results of meiosis with those of mitosis.

14. Given an organisms diploid number, determine how many tetrads are present in the first meiotic prophase.

15. Given an organisms diploid number, determine how many dyads are present in the second meiotic prophase and how many monads migrate to each pole during the second meiotic anaphase.

16. Ignoring details of spindle formation etc., diagram meiosis in a cell with any given number of chromosomes.

17. Explain why meiosis leads to significant genetic variation while mitosis does not.

18. Describe and compare polytene and lampbrush chromosomes.

Resources: Text Chapter 2, Cartoon Guide 56-68

Cellular/Organismal Reproduction- Mitosis, Meiosis

In order for a cell to have the knowledge about how to do its job (ex. Pancreas cell knowing how to make insulin) it must be given such knowledge upon its creation. This is of course the study of heredity.
-the knowledge is contained in a molecule called DNA

Two different mechanisms of inheritance at this level:
1. Single donor of information (ie. Each new cell uses the same information that its immediate ancestor used, since only one donor was involved the new cell will do things the same way its ancestor did; it's a clone)

-Asexual reproduction
-mitosis provides this opportunity

2. Two donors of information (ie. Each new cell (a zygote) receives information from two sources, typically a mom and a dad. This new cell has more options as to how to do things; it's variable, may not do things exactly the same way its ancestors did.)

-Sexual reproduction; biparental inheritance
-meiosis provides this opportunity

Cellular Reproduction
Purpose: Reproduction (bacteria, protists)
   Growth and Repair
   Maintain favorable surface area/ volume ratio
   Distribute instruction books

Two steps:
1. Mitosis- division of nuclear material
2. Cytokinesis

Cell Cycle, four stages Pg 20-22
1. G1- active growth and metabolism
2. S- DNA synthesis and duplication
3. G2- Synthesis of molecules in preparation of cell division

-G1, S, G2 are collectively referred to as INTERPHASE

4. Mitosis and Cytokinesis (four parts)
-mitotic chromosomes in this stage are highly condensed and coiled, thus distinct

   a. Prophase- chromosomes condense and organize; nuclear membrane disappears; spindle fibers attach
            -Prometaphase
   b. Metaphase- duplicated chromosomes line up along equator of cell. Spindles attach to
            each half (or one chromatid) of the duplicated chromosome.
   c. Anaphase- centromere is separated and paired chromosomes are pulled apart

d. Telophase- chromosomes uncoil, nuclear membrane reforming
-Cytokinesis then occurs producing two genetically identical daughter cells

Key Consideration-
When DNA is condensed for mitosis the information contained within is inaccessable

Coiled chromosomes classified according to position of centromere (the place spindle fibers attach) pg. 18
-Metacentric

-Acrocentric

-Telocentric

In eukaryotic organisms mitosis maintains chromosome number; repair and maintanance

Uncontrolled manifestation ----> Cancer

Each chromosome a double structure

After division daughters approx. ½ size of parent, however, nucleus not appreciably smaller

Organismal Reproduction and Meiosis

Sexual Reproduction- involves the fusion of genetic material (gametes) from two parents

1. To ensure proper chromosomal numbers in the zygote (fertilized egg), each gamete must have half or
diploid (1N) of the original diploid (2N) amount of each parents DNA
Meiosis- reductional division reducing the number of chromosomes by half, results in new
genetic combinations

Meiosis- 2 distinct divisions
1st reductional
2nd equational

Meiosis 1
   1. Prophase I- chromosomes condense and organize, matched or homologous
        chromosomes (one maternal, one paternal) are physically paired. This action creates Tetrads
        -segments of chromatids can cross-over within each chromosome pair (sisters)

2. Metaphase I- homologues (tetrads) line up at equator

3. Anaphase I- homologues separated into two groups with each group having a mixture
of maternal and paternal chromosomes

4. Telophase I- new haploid nuclei forming for two new daughter cells.

5. Interkinesis- no replication of DNA occurs because each chromosome is still
duplicated and consists of two chromatids)

Meiosis II
   1. Prophase II- chromosomes condense
   2. Metaphase II- chromosomes line up at equator
   3. Anaphase II- chromatids of each chromosome are separated
   4. Telophase II- each daughter cell from meiosis I will form two more cells for a total of
        four haploid cells

Meiosis Overview
-only occurs in formation of reproductive cells of sexually reproducing organisms

-reduces diploid to haploid
-genetic recombination (but without random array of one half of the chromosomes)

-crossing over occurs in the tetrad of homologous (sister) chromosomes in prophase of Meiosis I

-assures that each gamete receives only one copy of each pair of homologous chromosomes

-insures that zygote resulting from the egg and sperm union will have a different combo of alleles
than either parent

Total # of possible combos = 2n n= haploid # of chromosomes

In humans n=23 therefore 223 = 8,388,608

one crossover changes to 423 = 70,368,744,000,000 (this number is true for each parent)

Spermatogenesis and Oogenesis (pg.29-30)