Derek Lee
Mr. Hillegas
Ap Biology
4 February 2011
Chapter 10 Cell Reproduction Work
II.
1. Homologous and duplicated chromosomes – Together with 23 chromosomes from each parent, 23 homologous pairs are formed. These homologous pairs are duplicated in the processes of mitosis or meiosis for either cellular reproduction, growth, and repair, or sexual reproduction. The results of mitosis form 2 somatic diploid cells, while meiosis results in 4 autonomic haploid male or female gametes.
2. Kinetochore and Microtubule Organizing Center – During Metaphase I of meiosis when the tetrads line up long the metaphase plant, spindle fibers forms and MTs attach to kinetochores. These kinetochores shorten pulling apart the tetrads to opposites poles as the microtubules deploymerize.
3. Haploid and Somatic – Somatic cells include all cells except sex cells. They are the cells which undergo mitosis for cell reproduction, growth, and repair as opposed to autonomic, or sex cells which undergo mitosis, thus producing 4 gametes with a haploid number of chromosomes.
4. Nucleosome and Dehydration reaction- Nucleosomes consist of subunits of chromatin composed of a short length of DNA wrapped around a core of histone proteins. Dehydration reactions or condensation reactions refer to the use covalent bonds to join two molecules into a larger molecule. These bonds help coil histones as they form bonds between peptide bonds.
III. Sorting of Chromosomes
A. Meiosis I
1. Prophase 1- Chromosomes become visible as threadlike forms, each pairs with its homologue and swaps segments with it.
a. Microtubules form spindles, centrioles (if present) move to opposite sides of nuclear envelope.
b. Nuclear envelope begins to break up
2. Metaphase I – MTs attach to each type of chromosome, chromosomes line up at metaphase plate.
a. MTs begin to pull apart chromosomes
3. Anaphase I – Microtubules attached to each chromosome shorten and move toward spindle pole
a. Other MTs extend from poles and overlap at equator and push the poles father apart
b. Pushing driven by proteins
4. Telophase I – On of each type of chromosome on complete opposite sides of poles.
a. At some point the cytoplasm dives forming two haploid cells
b. All chromosomes are still duplicated
B. Meiosis II
1. Prophase II- Spindle forms in each haploid cell while MTs move one member of pair of centrioles to opposite sides of each cell.
a. MTOCs attach to one chromatid of each chromosome.
b. Its sister chromatid becomes tethered to opposite pole
2. Metaphase II – Chromosomes line at metaphase plate and MTs from both spindle poles begin to separate the sister chromatids
3. Anaphase II – Attachment between sister chromatids of each chromosome breaks
a. Each MTs continue to move chromosomes to opposite sides of the poles while MTs push the poles apart.
b. Chromosomes ends up near each pole, one of each type of chromosome is present in each parcel
4. Telophase II – Four nulei form as a new nuclear e nvelope encloses each cluster of chromosomes
a. After cytoplasmic division each of the daughter cells has a haploid number of chromosomes.
10.4 –
A. During prophase I of meiosis the duplicated chromosomes in a germ cell are in a thread like form with little space in between. 1. This tight, parallel orientation favors crossing over, a molecule interaction between a chromatid of one chromosomes and a chromatid of the homologous partner. 2. The DNA strands break and seal in such a way that the outcome results in two “nonsister” chromatids which leads to recombination among genes of homologous chromosomes. 3. This results in slightly different forms of alleles and thus each crossover event is a chance to swap slightly different versions of heritable information on gene products or produce variation in traits among offspring.
B. Metaphase I Alignments 1. During Metaphase I, Microtubules from both poles now align all duplicated chromosomes at the metaphase plate. 2. MTs attach to first chromosome they contact = random tethering and subsequent positioning of each pair of maternal and paternal chromosomes at metaphase plate. 3. During Anaphase I, duplicated chromosomes = move away from homologous partner = either partner can end up at either spindle pole. 4. Result of such events leads to different combination of maternal and paternal traits in each new generation.
10.6
While Mitosis maintains the parental chromosome number, meiosis halves it, to the haploid number. Miotic cell division is the basis of asexual reproduction among eukaryotes. It is the basis of growth and tissue repair of multicelled eukaryotic species. Meiotic cell division is a required step before the formation of gametes or sexual spores.
Similarities: Both processes undergo prophase, metaphase, anaphase, and telophase with similar processes and organelles i.e. MTOCs, spindle fibers, etc. Both have cytokinesis that occurs during telophase. Mitosis and meiosis only occurs in eukaryotic cells.
Differences: Occurrence of crossing over happens in meiosis but does not happen in mitosis.
-Meiosis occurs specifically in humans, animals, plants, and fungi, while mitosis happens in all organisms.
-Meiosis produces 4 daughter cells (4 haploid) while mitosis produces 2 (2 diploid) daughter cells.
-Meiosis produces genetic variation, is sexual reproduction, requires 2 divisions, pairs homologues and undergoes two series of prophase, metaphase, anaphase, and telophase. Mitosis produces identical genes, is asexual reproduction, undergoes 1 series of division, does not pair homologues, and undergoes one series of prophase, metaphase, anaphase, and telophase.
-Meiosis produces male and female eggs/sperms while mitosis produces all cells other than sex cells
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