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Flashcards in Meiosis And Recombination Deck (20):
0

What is the goal of mitosis

-end up with two identical cells to the original that are both diploid

1

What is the goal of meiosis?

-make four haploid gamete that are not identical to the original
-when they combine you get a diploid

2

Interphase of meiosis

-Where cells spend a majority of their time
-where all the genetic material is replicated

3

Prophase I

-centrioles migrate to their poles
-homologous chromosomes pair up and form a tetrad
-crossing over
-longest step in meiosis
-nuclear envelope is disappearing

4

Metaphase I

-tetrads line up across metaphase plate

5

Anaphase I

-pulling apart homologous sets of chromosomes
-pulling apart tetrads

6

Telophase I and cytokenesis

Makes two haploid cells

7

Prophase II

-nuclear envelope disappears
-centromeres migrate to opposite poles

8

Metaphase II

Sister chromatids line up on metaphase plate

9

Anaphase II

Sister chromatids are pulled apart

10

Telephase II and cytokenesis

End up with four haploid gametes

11

What do we pull apart in meisis I? II?

I:Tetrads
II: sister chromatids

12

Problems in meiosis

1. Nondisjunction
2. Translocation

13

Nondisjunction

-failure of tetrads to separate during meiosis i or sister chromatids in meiosis
-can lead to:
1. Down syndrome (trisomy 21)
2. Turner syndrome (x)
3. Kleinfelter syndrome (xxy)

14

Nondisjuction in meiosis I

Creates two trisomies and two monosomies

15

Nondisjunction in meiosis II

Makes one trisomy
One monosomy
Two normal

16

Is nondisjunction in meiosis I or II worse?

Meiosis I because there are no normal cells

17

Translocation

-movement of a segment of one chromosome to another non-homologous chromosome
-ex is down syndrome.. Chromosome 21 -> chromosome 14

18

Recombination

-single crossover
-double crossover

19

Linked genes

-genes on the same chromosome that probably will not undergo independent assortment
-the closer together on the chromosome the greater the linkage between genes
-the liklihood of recombination increases with distance between genes
---when genes are closer they are less likely to undergo recombination and are more likely linked