Meiosis and Genetic Variation

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  • Created by: Alice
  • Created on: 28-05-14 12:10
What is a gene?
Section of DNA which codes for a polypeptide
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What is a locus?
Positioning of gene on a chromosome/DNA
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What is an allele?
Particular type of gene
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What is Meiosis?
Reproduction of sex cells (gametes) through sexual reproduction, forming zygotes.
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What is Mitosis?
Reproduction of body cells - for growth and repair - somatic cells
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What is "diploid"?
23 pairs of chromosomes in body cells (somatic)
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What is "haploid"?
23 chromosomes - Gamete
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What is the normal diploid number in humans?
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What is the normal haploid number in humans?
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What are pairs of chromosomes called?
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Describe the process of Meiosis up to the start of Meiosis 2.
Homologous chromosomes pair up. Crossing over occurs where chromatids are broken and attached to homologous chromosome in Meiosis 1. Two daughter cells result from 1st mitotic division with 1 chromosome from each pair.
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Describe the process of Meiosis after Meiosis 2.
Meiosis 2 occurs - chromatids move apart, come apart at centromere. 4 daughter cells formed with 1 chromatid in each.
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What are the three ways that variation in Meiosis occurs?
Independent segregation, random fertilisation, chromatid crossing over
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How does independent segregation give variation?
Homologous chromosomes line up randomly during Meiosis 1 and divide between 2 daughter cells.
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Chromatid crossing over exchanges information. How does recombination by crossing over work?
Chromatids twist around each other many times. Tension created, portions break off. Broken portions rejoin with homologous partner making new genetic combinations.
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Card 2


What is a locus?


Positioning of gene on a chromosome/DNA

Card 3


What is an allele?


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Card 4


What is Meiosis?


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Card 5


What is Mitosis?


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