What Would Happen If Crossing Over Didn’t Occur During Meiosis? – A Discussion on the Importance of Genetic Diversity and Evolutionary Adaptation

PART C – Crossing over and genetic variationAssume that an organism exists in which crossing over does not occur, but that all other processes associated with meiosis occur normally. Consider how the absence of crossing over would affect the outcome of meiosis.If crossing over did not occur, which of the following statements about meiosis would be true? Select all that apply.

There would be less genetic variation among gametes.[Crossing over contributes significantly to the genetic variation seen in gametes. This is because the exchange of maternal and paternal genes between the nonsister chromatids of a homologous chromosome pair creates recombinant chromosomes with unique combinations of alleles. However, crossing over is not the only process that introduces genetic variation in meiosis I. The independent assortment of homologous chromosomes (which are never identical) in meiosis I produces daughter cells that differ from each other.The effect of crossing over on genetic variation is shown below. Without crossing over, sister chromatids remain identical and thus, pairs of daughter cells would be identical. With crossing over, however, all four daughter cells are genetically unique.]

If crossing over did not occur during meiosis, the following statements would be true:

1. There would be no exchange of genetic information between homologous chromosomes, which would lead to a lack of genetic variation in the resulting gametes.

2. The resulting gametes would contain only parental chromosomes, identical to the original cell before meiosis, which would result in a reduced ability for the offspring to adapt to changing environmental conditions.

3. The process of meiosis would still occur, but the resulting gametes would have the same genetic makeup as the parent cell.

Therefore, the absence of crossing over during meiosis would significantly reduce genetic diversity and may have negative impacts on the survival and reproduction of the organism in changing environments.

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