Chapter 10 - MEIOSIS

1. Textbook website: http://www.brookscole.com/biology
   1. chapter by chapter resources
      1. chapter/outlines/ch10.html
      2. chapter/quizzes/ch10
      3. flash cards-select from resources for chapter 10.
2. On-Line Biology Book by M. J. Farabee 
   1. Cell Division: Meiosis and Sexual Reproduction 
3. Kimball's Biology Pages
   1. Chromosomes from Kimball's Biology Pages
   2. Meiosis from Kimball's Biology Pages
   3. Crossing Over and Recombination from Kimball's Biology Pages
4. The Biology Project  an interactive online resource for learning biology, developed at The University of Arizona
   1. Meiosis
      1. reproduction
      2. Chromosomes in a Diploid Cell
      3. Meiosis 1 & 2
      4. Comparing Mitosis and Meiosis
      5. Test Yourself 
5. MIT Biology Hypertext 
   1. Meiosis
6. North Harris College Mitosis

Octopus Sex and Other Stories 

1. Octopus mating rituals 
2. Slipper limpets [Fig. 10.1a] 
3. Aphids [Fig, 10.1b]

10.1 -- COMPARING SEXUAL WITH ASEXUAL REPRODUCTION

10.1 – COMPARING SEXUAL AND ASEXUAL REPRODUCTION 

1. Asexual Reproduction 
   1. Offspring are produced by a single parent
   2.  Genes are identical to parent and siblings
2. Sexual Reproduction 
   1. each parent contributes one gene for each trait
   2. Alleles
   3. Variation in traits

10.2 – HOW MEIOSIS HALVES THE CHROMOSOME NUMBER

1. Think "Homologues" 
   1. Meiosis: reduces the number of chromosomes (chromosome number) and produces gametes [Fig. 10.2]
   2. Homologous chromosomes: 23 pairs in humans [Fig. 10.3] 
   3. diploid (2N) cells become haploid (N) 
2. Two Divisions, Not One 
   1. two successive cell divisions --> 4 haploid cells (gamete or spore) 
   2. independent assortment and crossing over. 
   3. fertilization: formation of zygote with full diploid number.

10.3- 10.4 - 10.5 – THE STAGES OF MEIOSIS [Fig. 10.4] 

1. First Meiotic Division (Meiosis I)
   1. homologous chromosomes separate and are distributed to separate nuclei 
   2. Stages
      1.  Prophase I [Fig. 10.5] 
         1. each chromosome consists of two chromatids
         2. synapsis
         3. crossing over [fig. 10.5]
      2. metaphase I 
         1. tetrads line up along spindle
         2. random arrangement of alignment [fig 10.6]
      3. anaphase I
         1. homologous chromosomes separate
      4. telophase I
         1. two haploid cells,  2 chromatids /chromosome
2. interkinesis
3. Second Meiotic Division (Meiosis II)
   1. separation of sister chromatids at centromeres 
   2. stages
      1. Prophase II
      2. metaphase II
      3. anaphase II
      4. telophase II 
         1. haploid gamete or spore

10.5 – FROM GAMETES TO OFFSPRING 

1. Position of Mitosis and Meiosis in Various Eukaryotes [fig 10.7] 
   1. Simple eukaryotes can be regularly haploid
   2. Plants (and some algae): alternation of generations: 
      1. Diploid sporophyte plant forms spores by meiosis
      2. Spores divide mitotically to form haploid gametophytes 
      3. Gameophyte plants produce gametes mitotically
      4.  Gametes fuse to form a zygote which forms a sporophyte by mitosis
      5. in higher plants, the haploid gametophyte is small and inconspicuous
   3. Animals
      1. diploid somatic cells
      2. haploid gametes 
      3. Spermatogenesis [fig 10.8]: four sperm
      4. Oogenesis [fig 10.09]:  three polar bodies and an ovum

IMPORTANCE OF MEIOSIS 

1. independent assortment --> 2^N combinations of gametes per parent
2. (2N)² possible zygotes 
3. Humans N=23; 8,388,608 kinds of gametes; 70,368,744,000,000 kinds of zygotes 
4. Crossing over: vastly increases variability; possibility of genetically different offspring
   1.  with just 1 crossing over per chromosome, there are 4 possible chromatids; 4N possible gametes 
   2. for humans one crossing oveer per chromosome --> 70,368,744,000,000 kinds of gametes; 4.95 X 10²⁷ zygotes

10.6 – MITOSIS AND MEIOSIS COMPARED

KEY TERMS FOR CHAPTER 10

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