Question

The results of a test cross reveal that all the offspring resemble the parent being tested. This parent must be
A. Heterozygous
B. Homozygous
C. Haploid
D. None of the above

Answer 1

A cross of a homozygous recessive individual with an individual with unknown genotypes is called test cross. It is done to determine the person’s genotype by looking at the phenotypes of offspring.

Complete answer:
Homozygous: if an individual has two similar alleles of a gene, he has a homozygous genotype.
Heterozygous: If an individual has two different alleles of a gene, he has a heterozygous genotype.
Ifan organism carries two copies of the same dominant allele, he is homozygous dominant.
If it carries two copies of the same recessive allele, he is homozygous recessive.
A test cross is the hypothetical breeding between an individual with an unknown genotype and a known homozygous recessive individual.
If the offsprings resemble the person being tested, it means the individual is homozygous dominant.

So, the correct option is B. Homozygous

Note: As we know alleles are alternative forms of a gene at a locus.
If an allele overpowers the other allele’s expression (when both of them are expressed together) –then it can be said that the allele which overpowers is dominant while the one which is overpowered is recessive.