Two genes R and Y are located very close together on the chromosomal linkage map of the maize plant. When RRYY and rryy parents are crossed and the resulting F_1 is test-crossed with rryy, the progeny will show

NEET Biology question

Two genes and are located very close together on the chromosomal linkage map of the maize plant. When and parents are crossed and the resulting is test-crossed with , the progeny will show

(A)A great excess of parental-type ( and ) phenotypes over recombinant-type ( and ) phenotypesCorrect
(B)All four phenotypic classes in equal () proportion, since the genes assort independently
(C)Only two phenotypic classes, in a ratio
(D)A great excess of recombinant-type phenotypes over parental-type phenotypes

Answer: (A)

Solution

Because genes and are very closely linked on the same chromosome, crossing over between them during meiosis is rare, so the test-cross progeny show a marked excess of parental-type combinations ( and ) over recombinant-type

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Question ID VK-119545