Question

In yeast, what are the recombinant genotypes that could form from a cross between two true breeding stocks, one which displays phenotype a and the other which displays phenotype b?

A B and A B a b and a b a B and A b
a b and A B A B and A b a B and a B a b and A b

Answer 1

Recombinant genotypes are the products of meiosis with allelic combinations different from those of haploid parents that used in particular crosses

In case of cross AB and AB , ab and ab & aB and aB no recombinant genotype gamet are produed beause no meiosis occur.

In case of aB and Ab

aB . Ab

a/A . B/b

after Meiosis

aB, ab, AB, Ab four gamets are fromed in which two AB and Ab are recombinant type

In case of ab and AB

ab . AB

a/A . b/B

after meiosis

aB, ab, AB, Ab four gamets are formed in wich aB and Ab are recombinant type

In case AB and Ab

AB . Ab

A/A . B/b

after meiosis

AB, Ab two type parental type of gamets are formed.

In case ab and Ab

ab . Ab

a/A . b/b

after Meiosis

ab and Ab gamets are produed and both are parental type

Hence only aB and Ab & ab and AB combination are recombinant type genotype produced.