Meiosis 2: - Splitting chromatids - n --> n+n: end results is 4 haploid cells
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Prophase 1
Nuclear membrane disappears
Homologous pairs stay together
Crossing over creates variation
Spindle appears
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Metaphase 1
Chromosome line up on the equator in pairs
Homologous pairs still together
Each centriole connects a spindle fibre to one member of the pair
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Anaphase 1
Spindle fibers pull the homologous pairs apart
Sister chromatids stay attached!
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Telophase 1
Nuclear membranes form
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Cytokinesis
Cytoplasm splits
Each cell is now haploid
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Prophase 2
Nuclear membrane disappears
Spindle forms
No crossing over!
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Metaphase 2
Chromosome line up at the equator
Each chromosome connect to two spindle fibers
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Anaphase 2
Chromatids are pulled apart
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Telophase 2
Nuclear membranes form
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Cytokinesis
Cytoplasm splits
4 unique haploid cells
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GENETIC VARIATION
What are the five sources of genetic variation?
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An ejaculation of a healthy man consists of 2-5 million sperm cells. Independent assortment has led to a huge genetic variation. Will all possible gametes be present in this ejaculation?
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MUTATIONS
Alterations in the genome of an organism:
They can be spontaneous (molecular decay)
Due to environmental influences (radiation, mutagens)
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What are the five sources of genetic variation?
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Learning objectives
List and describe the phases of meiosis
Describe changes in number of chromosomes during the steps of meiosis
Describe changes in DNA content during the steps of meiosis