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BiologyGenetics10 minIntermediate

Meiosis Crossing Over

Map homologous chromosomes, chromatids, and exchange points that create new allele combinations.

Annotated teaching image of homologous chromosomes crossing over during meiosis.
1

Cell nucleus

Compartment where chromosomes pair early in meiosis.

Crossing over happens when homologous chromosomes pair during meiosis I. DNA segments are exchanged between non-sister chromatids, producing chromosomes with new combinations of alleles.

This process helps explain why offspring are not exact copies of either parent, even when they inherit one chromosome from each.

Key Idea

Meiosis creates variation by reshuffling existing genetic information before gametes are formed.