In: Biology
Individuals from two separate true-breeding strains of white deer mice are crossed yielding all grey offspring. White is recessive to gray color based on crossing mice from each strain with a grey mouse. Which of the following would best explain this result?
a. lethal alleles
b. multiple alleles
c. epistasis
d. complementation
e. incomplete dominance
incomplete dominance is when heterozygotes show intermediate phenotype compared to homozygotes.
lethal alleles: the presence of alleles ( some times in the homozygous condition) results in a lethal phenotype.
multiple alleles: there are more than 2 alleles at a locus.
Epistasis: one locus determines the phenotype, depending on whether it is homozygous recessive or dominant.
complementation: functional alleles of two genes are required to produce normal phenotype.
there are two genes that determine the gray phenotype.
Let the genes be A and B.
normal alleles are A and B, recessive alleles are a and b.
genotype of true breeding white mice strain 1 is AAbb and genotype of second white strain is aaBB.
aaBB * AAbb
AaBb ( gray mice)
when a true breeding gray mice is crossed with white mice
AABB * aaBB
AaBB
all the progenies are gray so the gray phenotype is dominant to white phenotype.
so the answer is d) complementation.