9.2- Meiosis and genetic variation

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  • Created by: Megan2413
  • Created on: 13-06-17 17:14
What is meiosis?
A form of cell division which produces four daughter haploid gametes,
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What are the two stages in meiosis called?
Mieosis 1 and meiosis 2
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What occurs during meiosis 1?
It is the first division by which homologous chromosomes pair up and their chromatids wrap around each other during crossing-over and recombination. This division separates the replicated homologous pairs into two daughter cells
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What occurs during meiosis 2?
This is the second cell division by which the sister chromatids are separated to form four daughter cells
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What types of cells does meiosis 2 produce?
Haploid gametes
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What two things does meiosis achieve?
- Produces haploid cells so when two gametes fuse they form a diploid cell - Genetic variation among offspring
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What three forms of genetic variation is due to meiosis?
- Independant segregation of homologous chromosomes - Crossing over and recombination - Variety from new genetic combinations
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How does independant segregation of homologous chromosomes increase genetic variation?
- Homologous pairs line up randomly in the equator of the cell before meiosis 1 - During meiosis 1 homologous pairs are separated randomly into 2 daughter cells
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When does crossing over and recombination occur?
During meiosis 1
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What happens during crossing over?
The chromatids of each pair become twisted round one another creating tensions which cause portions of the chromatids to break off
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What happens during recombination?
- These broken pieces may region with the chromatid of their homologous partner
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How do we get variety in homologous chromosomes?
Both chromatids in each homologous pair contain the same genes, but they may have different alleles
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What formula is usd to determine the number of pairs of chromosome combinations in a meiosis daughter cell?
2^n
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What does n=?
The number of pairs of homologous chromosomes
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What is the formula to determine the number of chromosome combinations after fertilisation of two gametes?
(2^n)^2
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Card 2

Front

What are the two stages in meiosis called?

Back

Mieosis 1 and meiosis 2

Card 3

Front

What occurs during meiosis 1?

Back

Preview of the front of card 3

Card 4

Front

What occurs during meiosis 2?

Back

Preview of the front of card 4

Card 5

Front

What types of cells does meiosis 2 produce?

Back

Preview of the front of card 5
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