Use the following information to answer the question.
A plantlike organism on the planet Pandora can have three recessive genetic traits: bluish leaves, due to an allele (a) of gene A; a feathered stem, due to an allele (b) of gene B; and hollow roots due to an allele (c) of gene C. The three genes are linked and recombine.
A geneticist performed a testcross with an organism that had been found to be heterozygous for the three recessive traits, and she was able to identify progeny of the following phenotypic distribution (+ = wild type):

What is the greatest benefit of having used a testcross for this experiment?
A) The homozygous recessive parents are obvious to the naked eye.
B) The homozygous parents are the only ones whose crossovers make a difference.
C) The phenotypes of the progeny reveal the allelic content of the gamete from the heterozygous parent.
D) All of the progeny will be heterozygous.

Question

Use the following information to answer the question.
A plantlike organism on the planet Pandora can have three recessive genetic traits: bluish leaves, due to an allele (a) of gene A; a feathered stem, due to an allele (b) of gene B; and hollow roots due to an allele (c) of gene C. The three genes are linked and recombine.
A geneticist performed a testcross with an organism that had been found to be heterozygous for the three recessive traits, and she was able to identify progeny of the following phenotypic distribution (+ = wild type):

What is the greatest benefit of having used a testcross for this experiment?
A) The homozygous recessive parents are obvious to the naked eye. 
B) The homozygous parents are the only ones whose crossovers make a difference. 
C) The phenotypes of the progeny reveal the allelic content of the gamete from the heterozygous parent. 
D) All of the progeny will be heterozygous.

Quizplus · Accepted Answer

A testcross is used to determine the genotype of an individual with dominant phenotype but unknown genotype. In this experiment, the geneticist performed a testcross with an organism that had been found to be heterozygous for the three recessive traits. By crossing the heterozygous parent with a homozygous recessive parent for all three traits, the phenotypes of the progeny reveal the allelic content of the gamete from the heterozygous parent. Therefore, the greatest benefit of using a testcross in this experiment is that it allows for the determination of the allelic content of the heterozygous parent's gametes.

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