Campbell Problem 13

Molecular Genetics Problem 13

13. Assume genes A and B are linked and are 50 map units apart. An individual heterozygous at both loci is crossed with an individual who is homozygous recessive at both loci. (a) What percentage of the offspring will show phenotypes resulting from crossovers? (b) If you did not know genes A and B were linked, how would you interpret the results of this cross?

 

a) 50 % because when the loci are at opposite ends of a chromosome they behave as if they were on different chromosomes.

Beginning with 100%

recombination results in 50%

and 50%

The resulting cross gives results almost identical to a normal Mendelian dihybrid cross, which can be symbolized as follows:

 
expected genotypes

recombinant genotypes

b) You would assume that these genes were on separate chromosomes since they appear to segregate independently even though they are linked.

 

BACK