Download 11.2 Meiosis

11.2 Meiosis
I. What Happens During Meiosis
A. Meiosis halves the number of chromosomes
1. Crossing Over
a. paired chromosomes exchange segments of DNA
2. Skipping Replication
a. Only one replication of DNA but two divisions
II. Meiosis I
A. Prophase I
1. Chromosomes condense, nuclear envelope disappears,
& crossing over occurs
B. Metaphase I
1. Chromosomes moved to equator by spindle fibers.
2. Two chromatids remain together
3. Independent assortment
a. Random distribution of homologous chromosomes
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C. Anaphase I
1. Homologous chromosomes separate & are pulled to
opposite ends
2. Chromosomes do not separate at centromeres
D. Telophase I
1. The two new cells contain half the number of
chromosomes
2. Called reduction division
III. Meiosis II
A. Identical to stages of mitosis with a few exceptions
1. Chromosomes do not replicate before they divide
2. In the end 4 haploid cells are created
IV. Genetic Recombination
A. Two chromosomes no longer contain identical genetic
material
B. Allow for genetic variation which can impact how fast
species evolve
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