Solutions For An Introduction to Genetic Analysis Chapter 3 Problem 28P

The genes that determine Hair length are as follows:

• Short = H

• Long = h

The Short (H) is dominant over Long (h). Thus, the genotypes, which express Short and Long phenotype, are as follows:

Short:

• HH- Homozygous dominant

• Hh- Heterozygous dominant

Long:

• hh- Homozygous recessive

The seven mating’s with the above phenotypes give following number of progeny.

Mating	Parental phenotypes	Number of progeny (%)
		Dark, Short	Dark, Long	Albino, Short	Albino, Long
a.	Dark, Short × Dark, Short	55	19.375	18.125	7.5
b.	Dark, Short × Dark, Long	51.4	48.6	0	0
c.	Dark, Short × Albino, Short	51.2	0	48.8	0
d.	Albino, Short × Albino, Short	0	0	76.3	23.7
e.	Dark, Long× Dark, Long	0	73.8	0	26.2
f.	Dark, Short × Dark, Short	73.8	26.2	0	0
g.	Dark, Short × Dark, Long	38.3	37.0	12.3	12.3

The genotypes, which shows

• Dark, Short: CCHH, CCHh, CcHH and CcHh

• Dark, Long: CChh and Cchh

• Albino, Short: ccHH and ccHh

• Albino, long: cchh

The cross of “mating-a” (Dark, Short × Dark, Short) is as follows:

Thus, the probable genotypes of parents for mating-a, are as follows: CcHh × CcHh.

The cross of “mating-b” (Dark, Short × Dark, Long) is as follows:

Thus, the probable genotypes of parents for mating-b, are as follows: CCHh × Cchh.

The cross of “mating-c” (Dark, Short × Albino, Short) is as follows:

Thus, the probable genotypes of parents for mating-c, are as follows: CcHH × ccHH.

The cross of “mating-d” (Albino, Short × Albino, Short) is as follows:

Thus, the probable genotypes of parents for mating-d, are as follows: ccHh × ccHh.

The cross of “mating-e” (Dark, Long× Dark, Long) is as follows:

Thus, the probable genotypes of parents for mating-e are as follows: Cchh × Cchh.

The cross of “mating-f” (Dark, Short × Dark, Short) is as follows:

Thus, the probable genotypes of parents for mating-f are as follows: CCHh × CcHh.

The cross of “mating-g” (Dark, Short × Dark, Long) is as follows:

Thus, the probable genotypes of parents for mating-g are as follows: CcHh × Cchh.