a cross between an organism whose genotype for a certain trait is unknown and an organism that is homozygous recessive for that trait so the unknown genotype can be determined from that of the offspring
To perform a testcross, scientists cross the organism with an unknown genotype with a homozygous recessive organism. This allows researchers to determine the unknown genotype based on the phenotypic ratios observed in the offspring.
If an individual is of the dominant phenotype, its genotype can be either AA or Aa (letter A picked for demonstration's sake). To do a good test cross, we have to be able to unambiguously tell which one of the genotypes the individual is. The best test cross would be conducted with a homozygous recessive (aa) individual. This way, if the cross generates 100% dominant phenotype, then the original individual was homozygous dominant. If the cross generates 50% dominant and 50% recessive phenotype, then the original individual was heterozygous.
Tt
Not necessarily. The offspring being alike and resembling the organism being tested is an indication of the parent being homozygous for the traits being tested, but it is not a definitive proof. Further tests or observations would be needed to confirm the parent's genotype.
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genotype
There are eight possible phenotypic classes that can be generated from a three-point testcross: two parental classes and six recombinant classes.
testcross
It would be around 50%.
Do a testcross with a homozygous recessive plant.
Do a testcross with a homozygous recessive plant.
homozygous recessive
testcross
Do a testcross with a homozygous recessive plant.
Do a testcross with a homozygous recessive plant.
Do a testcross with a homozygous recessive plant.
Do a testcross with a homozygous recessive plant.