Solutions For An Introduction to Genetic Analysis Chapter 17 Problem 46P

There are five deletions present along with 6 recessive alleles a – f. When the deletions are combined with each recessive allele; the results seen are tabulated as shown:

Based on the known sequence of deletions we can find out the sequence of the recessive genes. This process is known as deletion mapping. This technique is based on the expression of the mutant recessive phenotype in the presence of a deletion of the corresponding homologue.

When we compare deletions 1 and 2 in the table, a “+”sign for deletion 2 and “b” allele indicates that “b” is ahead of “a”. The approximate order is b-a-c.

When we compare deletions 2 and 3 in the table, the “-” sign for deletion 3 and “e” allele indicates that it lies to the right. The approximate order would be b-a-c-e.

When we compare deletions 3 and 4 in the table, the allele “a” lies to the left of “c” and alleles “e” and “d” lie to the right of “e”. The approximate order is b-a-c-e-d.

When we compare deletions 4 and 5 in the table, the allele “f” is more to the right than “d”. Hence, the correct order is b-a-c-e-d-f.

Hence, the order of alleles with the bands seen on the chromosome would be represented as:

1 - b

2 - a

3 - c

4 - e

5 - d

6 - f