In a Haploid Fungus,genes a and B Are Located on Chromosome

question 42

Multiple Choice

In a haploid fungus,genes a and b are located on chromosome 2 and 7,respectively.A cross is performed between a strain that is genotypically a;b and has normal chromosomes,and a strain that is genotypically wild type but has a reciprocal translocation between chromosomes 2 and 7.If crossing over never occurs in this fungus,what is the expected proportion of tetrads resulting from the cross? $$\begin{array} { l l l l l l } & \text { Tetrad I } & \text { Tetrad 2 } & \text { Tetrad 3 } & \text { Tetrad 4 } & \text { Tetrad 5 } \\\text { Spore 1 } & \text { aborted } & a ; b & A ; B & A ; B & A ; B \\\text { Spore 2 } & \text { aborted } & a ; b & A ; B & A ; B & \text { aborted } \\\text { Spore 3 } & \text { aborted } & \text { aborted } & \text { abarted } & a ; b & a ; b \\\text { Spore 4 } & \text { aborted } & \text { aborted } & \text { aborted } & a ; b & \text { aborted }\end{array}$$

• A)All five tetrads will be present,in equal proportions.
• B)Only tetrads 1 and 4 will be present,in a 1:1 ratio.
• C)Only tetrads 2 and 3 will be present,in a 1:1 ratio.
• D)Only tetrads 2,3,and 5 will be present,in a 1:1:2 ratio.
• E)Only tetrad 5 will be present.