Independent Assortment, Crossing Over, and Genetic Variation (OCR A-Level Biology A): Flashcards
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2 mechanisms generating genetic variation in meiosis
2 mechanisms generating genetic variation in meiosis
Independent assortment and crossing over
Independent assortment
Independent assortment
Random distribution of chromosomes from homologous pairs
When independent assortment occurs
When independent assortment occurs
During meiosis I (first meiotic division)
Formula for chromosome combinations (n=homologous pairs)
Formula for chromosome combinations (n=homologous pairs)
2^n
Human gamete combinations from independent assortment
Human gamete combinations from independent assortment
Over 8 million (approx. 8.4 million)
Crossing over
Crossing over
Exchange of genetic material between homologous chromosomes
When crossing over occurs
When crossing over occurs
During prophase I of meiosis
Chiasmata
Chiasmata
Points where chromatids cross and exchange genetic material
Bivalent
Bivalent
Paired homologous chromosomes
Typical number of chiasmata per bivalent
Typical number of chiasmata per bivalent
Two, three, or more