A test cross between a plant of genotype PpSs and the tester of genotype ppss gi
ID: 86078 • Letter: A
Question
A test cross between a plant of genotype PpSs and the tester of genotype ppss gives the following numbers of progeny in four phenotypic types. 14:86:84:16 (purple flower + smooth seed coat: purple flower + wrinkled seed coat: white flower + smooth seed coat: white flower + wrinkled seed coat). a) What is the expected ratio of progeny phenotypes assuming independent assortment of alleles? b) Explain how ratios of progeny show that the two genes are linked. c) How many map units separate the purple and smooth genes? Show your calculations.
Explanation / Answer
Answer:
The expected ratio is 1:1:1:1_____________________________(Ans a)
Such ratio of 1:1:1:1 indicates that the two genes are unlinked. But the actual ratio obtained is 14:86:84:16. So, the genes are linked._______________________________________(Ans b)
Recombinant frequency between P and S = 86 + 84 / 200 = 170 / 200 = 0.85 map units_______________(Ans c)
PS Ps pS ps ps PpSs (purple smooth) Ppss (purple wrinkled) ppSs (white smooth) ppss (white wrinkled)Related Questions
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