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How to find parents' genotypes from progeny phenotype frequencies? 
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#1
Sep1511, 06:37 AM

P: 53

Question: 8 phenotypes were observed as a result of a trihybrid cross. The frequencies of the phenotypes are
a+ b+ c = 570 a b c+ = 545 a+ b c+ = 17 a b+ c = 20 a+ b c = 140 a b+ c+ = 128 a+ b+ c+ = 65 a b c = 61 No other information is given. It is not even specified if it is a testcross. How to know if the genes were linked? Also, what are the possible genotypes of the parents? My attempt  The phenotypes with the two largest frequencies represent parental classes. Thus a+ b+ c and a b c+ are parental recombinant phenotypes. The phenotypes a+ b c+ and a b+ c are double recombinant phenotypes as these have the smallest frequencies. The other 4 are single recombinant phenotypes. But I do not know how to proceed from here. Suppose I calculate the % of all the recombinant (single and double) phenotypes and find it to be less than 50%, can I conclude that the genes were linked? 


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