alleryStart learning →In a test cross, the plant showing the dominant trait is crossed with which partner?
AA plant heterozygous at the same gene
BA plant of the same unknown genotype
CA plant homozygous dominant at that gene
DA plant homozygous recessive at that gene
Answer & Solution
Correct answer: D. A plant homozygous recessive at that gene
1. A test cross asks whether a dominant-looking organism is homozygous or heterozygous.
2. The partner chosen is homozygous recessive for the same characteristic.
3. That partner can only donate recessive alleles, so the offspring phenotypes reveal the unknown parent's alleles.
4. A homozygous dominant or heterozygous partner would mask the answer.
_Source: OpenStax Biology (1st ed., CC BY 4.0), Ch 12 "Mendel's Experiments and Heredity", section 12.2 Characteristics and Traits_
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