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Monohybrid crosses Original Scenario-Based Practice

Biology · Heredity · Biology · Mendelian Genetics

1 Biology practice questions on Monohybrid crosses. Questions built around original scenarios.

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Questions

  1. 1.

    A xenobiologist studying a subterranean cavern discovers a beetle species whose carapace emits either sapphire or amber bioluminescence governed by a single Mendelian gene. The allele for sapphire luminescence (B) is completely dominant to the allele for amber luminescence (b). When two sapphire-glowing beetles are crossed, their offspring consist of 298 sapphire-glowing individuals and 101 amber-glowing individuals. Based on these monohybrid cross results, which statement correctly identifies the parental genotypes and the genotypic ratio among the sapphire offspring?

    • A) Both parents are homozygous dominant (BB × BB), and all sapphire progeny are homozygous dominant (BB).
    • B) Both parents are heterozygous (Bb × Bb), and the sapphire progeny exhibit a genotypic ratio of 1 BB : 2 Bb.
    • C) One parent is heterozygous (Bb) and one is homozygous recessive (bb), and all sapphire progeny are heterozygous (Bb).
    • D) Both parents are heterozygous (Bb × Bb), and the sapphire progeny exhibit a genotypic ratio of 1 BB : 1 Bb.

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