If an organism of unknown genotype is crossed with a homzygous recessive organism and half of the offspring show the dominant phenotype and the other half of the offspring show the recessive phenotype, then the unknown genotype must be heterozygous (option D).
What is a test cross?
A test cross in genetics is the breeding of an individual with a phenotypically recessive individual, in order to determine the zygosity of the former by analysing proportions of offspring phenotypes.
According to this question, a testcross was performed by crossing an unknown genotype with a homozygous recessive organism.
However, half of the offspring show the dominant phenotype and the other half of the offspring show the recessive phenotype. This is due to the fact that the unknown genotype is heterozygous.
Learn more about testcross at: https://brainly.com/question/13241787
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