Biology / Unit 5 Bio 0987 short lesson, about 20 seconds
Crossing Over as a Source of Genetic Variation
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The idea
Crossing over creates new allele combinations along a single chromosome by exchanging segments between maternal and paternal homologs before they separate.
In practice
A chromosome entering meiosis with all maternal alleles can exit carrying a mix of maternal and paternal alleles after one crossover event.
Where people slip
Crossing over recombines existing alleles — it does not create new alleles by itself.
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