chapter 12 biology sixth edition raven/johnson (c) the mcgraw-hill companies, inc
TRANSCRIPT
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Chapter 12
BiologySixth Edition
Raven/Johnson
(c) The McGraw-Hill Companies, Inc.
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The purpose of meiosis is to produce haploid (n) cells from diploid (2n) cells.
Each haploid cell has only 1 type of each chromosome.
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2N
Male
Female
2N
Meiosis
Meiosis has an end point, unlike mitosis which is a cycle.
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Meiosis has two periods and consists of two cellular divisions.
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Phases of Meiosis:
Prophase I; Metaphase I; Anaphase I; Telophase I
Interkinesis
Prophase II; Metaphase II; Anaphase II; Telophase II
You need to know what is happening to the chromosomes at each of these phase!!
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Meiosis I – separates homologous chromosomes
Meiosis II – separates sister chromatids.
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Important meiotic events you need to know:
Synapsis; Crossing Over; Random Orientation
Prophase I Metaphase I
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Homologous chromosomes pair all along their length.
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Physical pieces of homologous chromosomes change chromosomes.
‘although you get you fathers copy of chromosome #1, chances are some of that chromosome contains some of your mothers genetic material’
Mother Father
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Chiasma – X shapes formed when homologous chromosomes are crossing over.
Homologous Chromosomes
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Because Chiasmata hold homologues together, microtubules only fuse to one side of the kinetochore.
Microtubules fuse to both sides of the kinetochore during mitosis.
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The End.