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The height of a type of bean plant is determined by five unlinked genes called A, B, C, D, and E. Each gene has two alleles: additive (uppercase letter) and nonadditive (lowercase letter). The shortest plants are 130 cm. The tallest plants are 220 cm. The genotypes are known for two bean plants. Plant 1 is genotype AABbccDdEE. Plant 2 is genotype aaBBCcDdEE.
-If the progeny plant resulting from an AbcdE gamete from plant 1(AABbccDdEE) and an aBcdE gamete from plant 2 (aaBBCcDdEE) was only 60 cm because of an allele in a gene other than A-E, what genetic phenomenon is at work?
A) A mutation occurred that is epistatic to the height genes because, no matter what genotype the plant has for the genes A-E, the phenotype is still 60 cm.
B) Crossing over occurred within the A-E region that created recombination in the progeny.
C) There must have been a change in the environment, such as low water, that caused the stunted growth in the plant.
D) The genes A-E do not actually work in an additive manner but rather in a dominant mode of inheritance.
E) Multiple alleles must be present in at least two of the loci involved.

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The height of a type of bean plant is determined by five unlinked genes called A, B, C, D, and E. Each gene has two alleles: additive (uppercase letter) and nonadditive (lowercase letter). The shortest plants are 130 cm. The tallest plants are 220 cm. The genotypes are known for two bean plants. Plant 1 is genotype AABbccDdEE. Plant 2 is genotype aaBBCcDdEE.
-If the progeny plant resulting from an AbcdE gamete from plant 1(AABbccDdEE) and an aBcdE gamete from plant 2 (aaBBCcDdEE) was only 60 cm because of an allele in a gene other than A-E, what genetic phenomenon is at work?
A) A mutation occurred that is epistatic to the height genes because, no matter what genotype the plant has for the genes A-E, the phenotype is still 60 cm.
B) Crossing over occurred within the A-E region that created recombination in the progeny.
C) There must have been a change in the environment, such as low water, that caused the stunted growth in the plant.
D) The genes A-E do not actually work in an additive manner but rather in a dominant mode of inheritance.
E) Multiple alleles must be present in at least two of the loci involved.

Quizplus · Accepted Answer

The progeny plant's height being 60 cm despite the additive effects of genes A-E suggests that a mutation in another gene is epistatic, overriding the expected phenotype.

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