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Crossing over Transitional Reasoning Practice

Biology · Heredity · Biology · Meiosis & Sexual Reproduction

1 Biology practice questions on Crossing over. Questions that build towards applied reasoning.

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  1. 1.

    In an individual with the genotype AB/ab, two gene loci are linked on the same pair of homologous chromosomes. A single primary meiocyte undergoes meiosis, during which a single reciprocal crossing over event occurs between these two loci involving two non-sister chromatids. If this cell completes meiosis without any non-disjunction or mutation, which of the following describes the genetic composition of the four resulting haploid gametes?

    • A) All four gametes will display recombinant combinations of alleles because crossing over alters every chromatid in the tetrad.
    • B) Crossing over fails to alter allele combinations in any gamete because homologous segments are merely realigned without exchange.
    • C) Two gametes will carry duplicated gene loci while the other two will lack both loci completely due to the exchange.
    • D) Exactly two gametes will possess recombinant genotypes (Ab and aB), while the remaining two will retain parental genotypes (AB and ab).

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