Cell repo lesson 6 meiosis.notebook
December 22, 2015
Aim: How is Meiosis different from mitosis?
Cell reproduction hw 1. Unit Test 1/6
2. Read pgs. 323 to 327 pay attention to figures. 1. Go over hw.
2. Notes on meiosis. 3. work in small groups lets mix it up!
Dec 18­7:11 PM
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Cell repo lesson 6 meiosis.notebook
December 22, 2015
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Purpose of Meiosis
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The process by which a germinal cell produces 4 cells (sex cells) with half of the number of chromosomes of the parent cell. It consists on two consecutive divisions; happens in the gonads of an organism. Male gonad = testicles Female gonad= ovary
The parent cell is diploid (complete number of chromosomes­2n) the 4 daughter sex cells (gametes)are haploid (n) http://vcell.ndsu.nodak.edu/animations/meiosis/movie­flash.htm
Dec 18­7:30 PM
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Cell repo lesson 6 meiosis.notebook
December 22, 2015
Homologous chromosomes.
homologous means that each one has the genetic information for the same characteristics.
Dec 18­8:18 PM
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Cell repo lesson 6 meiosis.notebook
December 22, 2015
The process of meiosis:
• Two divisions. Each division has the same phases as in mitosis. • In the first prophase the homologous chromosomes form a tetrad (label it in your copy) • Homologous chromosomes cross over, and then randomly interchange pieces. (label it)
• The resulting chromosomes contain different genetic information.
• At the end of the first division the number of chromosomes is reduced in half , but the chromosomes still contain the sister chromatids.
disjunction of homologous chromosomes
After the second division the two n cells produce 4 haploid cells (n) (?) genetically different from each other. The variation produced by meiosis is the key to the evolution of species.
Fertilization reestablishes the diploid number for the species, and mitosis and differentiation start taking place.
Dec 18­7:54 PM
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Cell repo lesson 6 meiosis.notebook
December 22, 2015
Testicle
Gonad
4 functional gametes
Spermatogenesis:
Dec 16­9:19 PM
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Cell repo lesson 6 meiosis.notebook
December 22, 2015
Oogenesis.
Ovary
Gonad
1 functional gamete or egg
Dec 16­9:33 PM
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Cell repo lesson 6 meiosis.notebook
December 22, 2015
Vocabulary review and new vocab. • Mitosis could be referred as mitotic cell division
• Meiosis could be referred as meiotic cell division
• Homologous chromosomes: Pair of chromosomes that control the same traits. One from each parent. • A Tetrad is a term that describes a pair of homologous chromosomes
• Synapsis occurs when the chromosomes in a tetrad join together
• Crossing over means that the homologuous chromosomes twist on each other and interchange pieces. • When the tetrads separate disjunction occurs. All sister chromatids are now genetically different from each other. • In Females one germ cell produces one egg. • Egg = ovum eggs = Ova
The sequence goes:
fertilization
Sperm + Egg Zygote Mitosis, cell differentiation and cell apoptosis Multicellular organism if an animal has 32 chromosomes in its muscle cells, How many does it have in its sperms?
Dec 16­9:54 PM
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