A true-breeding strain of tall soybean plants is crossed with a true-breeding strain of short soybean plants.All the offspring are short.These offspring are then crossed with each other to create an F₂ generation.If the height of soybean plants is due to a single gene, then of 200 F₂plants, _______ should be tall. A) 25 B) 50 C) 75 D) 100 E) 150

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Quizplus · Accepted Answer

If the height of soybean plants is due to a single gene, it means that tallness is dominant (represented by uppercase "B" allele) over shortness (represented by lowercase "b" allele). From the initial cross, we can infer that the tall parent was homozygous dominant (BB) and the short parent was homozygous recessive (bb). When they were crossed, all the offspring were heterozygous (Bb) for the height gene. The Bb offspring were then crossed with each other, resulting in a Punnett square with the following genotypes: BB, Bb, Bb, and bb in a 1:2:1 ratio. Only the BB offspring will be tall, so out of 200 plants, 50 (25%) of them should be tall.

A True-Breeding Strain of Tall Soybean Plants Is Crossed with a True-Breeding