5.2 Meiosis and Genetic Diversity
Notes
Variation comes from:
- Crossing over (prophase I): homologs swap segments.
- Independent assortment (metaphase I): homolog pairs line up randomly.
- Random fertilization: any sperm with any egg.
- Nondisjunction: chromosomes fail to separate, causing extra or missing chromosomes.
Practice
Crossing over happens during:
Homologs pair up.
With $n=3$ chromosome pairs, independent assortment gives how many combinations?
$2^3$.
Down syndrome (trisomy 21) results from:
An extra chromosome 21.
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