Genetic testing of an F1 hybrid Crossing an F1 individual with a homozygous recessive tester is referred to as which type of cross?
-
ATest cross
-
BRecessive cross
-
CCriss-cross
-
DPara-cross
-
EBackcross to a dominant parent
Answer
Correct Answer: Test cross
Explanation
Introduction / Context:Breeders and geneticists use specific crosses to reveal genotype. A test cross helps determine whether an individual with a dominant phenotype is homozygous dominant or heterozygous.
Given Data / Assumptions:
- F1 is typically heterozygous when derived from two true-breeding parents.
- The tester is homozygous recessive for the locus of interest.
Concept / Approach:In a test cross, mating with a homozygous recessive reveals the gametes contributed by the tested parent, because the tester contributes only recessive alleles. Offspring phenotypes therefore directly reflect the tested parent’s genotype.
Step-by-Step Solution:
Define the cross: F1 (e.g., Aa) x tester (aa).Predict offspring: 1 Aa (dominant phenotype) : 1 aa (recessive phenotype) if F1 is heterozygous.Name of such cross: test cross.Verification / Alternative check:Any genetics manual describes test crosses for mapping and genotype assessment.
Why Other Options Are Wrong:
- “Recessive cross” is not standard terminology.
- “Criss-cross” refers to sex-linked transmission patterns, not this cross.
- “Para-cross” is not a standard genetic term.
- Backcross to a dominant parent is a different design and does not reveal hidden recessive alleles.
Common Pitfalls:Confusing backcross (to either parent) with a test cross (specifically to recessive).
Final Answer:Test cross