Meiosis
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What is a diploid and haploid cell?
Diploid - 2 chromosomes of each type due to gamete fusion Haploid - 1/2 the chromosomes in a diploid (gamete)
Features of homologous chromosomes? (6)
• Matching set of chromosomes • Same gene, differing alleles • Similar length • Centromere in the same place • Same bonding pattern • Pair up in meiosis
What is an allele?
Different versions of the same gene
Why do we need meiosis and how does it function? (2)
• Haploids to maintain diploids - Results in genetic variation
What occurs in prophase 1? (3)
• Bivalents form • Crossing over occurs • Independent assortment
What happens in metaphase 1? (2)
Homologous chromosomes pulled to poles - Crossing over (genes exchanged)
What happens in anaphase 1? (2)
• Exchange of DNA - Points of which chromatids break and rejoin are called chiasmata
What occurs in meiosis II? (4)
• Metaphase II • More independent assortment • Telophase II • Haploid cells
What results in genetic variation?
• Independent assortment • Random fertilisation - unique combination of genes • Gene mutation - silent mutations