Mendel crossed AABB with aabb individuals, where B = smooth, b = wrinkled, A = yellow, and a = green. What was the genotypic ratio of the F₁ generation? A) all AAbb B) one-half AAbb and one-half aaBB C) all AaBb D) all AABB

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Quizplus · Accepted Answer

The F1 generation will be all AaBb individuals, since they will all have the genotype AaBb due to the fact that they each received one copy of allele A and one copy of allele B from their parents (AABB and aabb). When two AaBb individuals are crossed, there are different possible combinations of alleles that can be passed on to the offspring. Using a Punnett square for this cross, the genotypic ratio of the F₁ generation will be 1 AABB : 2 AaBB : 2 aaBb : 1 aabb. However, this ratio can be simplified by taking into account the fact that the AaBb individuals are heterozygous for both traits and will therefore generate equal numbers of gametes carrying the dominant allele and those carrying the recessive allele. Thus, the ratio can also be expressed as 1 dominant homozygous : 2 dominant heterozygous : 1 recessive homozygous, which means that half of the offspring will be AaBb (dominant heterozygous) and the other half will be either AABB (dominant homozygous) or aabb (recessive homozygous). Therefore, choice C (all AaBb) is the best answer.

Mendel Crossed AABB with Aabb Individuals, Where B = Smooth