Solutions For An Introduction to Genetic Analysis Chapter 6 Problem 22P

The cross-2 is made between a black and an albino individual, but the progeny has 1:1 ratio of black and sepia phenotypes. It is a complete dominance phenomenon (test cross). So, the genotype of the black parent should be heterozygous (bs) and the albino parent is (aa) and the cross is as follows:

Therefore, the black is dominant over sepia.

The cross-3 is made between two cream individuals, but the progeny has 3:1 ratio of cream and albino phenotypes. It is a complete dominance phenomenon. So, the genotype of both cream parents should be heterozygous (ca) and the cross is as follows:

Therefore, the cream is dominant over albino.

The cross-4 is made between a cream and sepia individual, but the progeny has 1: 2: 1 ratio of cream, sepia and albino phenotypes. It is an incomplete dominance phenomenon. So, the genotype of the cream parent should be heterozygous (ca) and the sepia parent is (sa) and the cross is as follows:

Therefore, the sepia is dominant over albino and cream.

The cross-5 is made between a black and albino individual, but the progeny has 1: 1 ratio of black and cream phenotypes. It is a complete dominance phenomenon (test cross). So, the genotype of the black parent should be heterozygous (bc) and the albino parent is (aa) and the cross is as follows:

Therefore, the black is dominant over cream.

The cross-6 is made between a black and cream individual, but the progeny has 1: 1 ratio of black and sepia phenotypes. It is a complete dominance phenomenon (test cross). So, the genotype of the black parent should be heterozygous (bs) and the cream parent could be (cc or ca) and the cross is as follows:

Therefore, the black is dominant over sepia and the sepia is dominant over cream and albino.

The cross-7 is made between a black and sepia individual, but the progeny has 1: 1 ratio of black and sepia phenotypes. It is a complete dominance phenomenon (test cross). So, the genotype of the black parent should be heterozygous (bs) and the sepia parent could be (ss, sc or sa) and the cross is as follows:

Therefore, the black is dominant over sepia and the sepia is dominant over cream and albino.

The cross-8 is made between a black and sepia individual, but the progeny has 1: 2: 1 ratio of sepia, black and cream phenotypes. It is an incomplete dominance phenomenon. So, the genotype of the black parent should be heterozygous (bc) and the sepia parent is (sc) and the cross is as follows:

Therefore, the black is dominant over sepia and the sepia is dominant over cream.

The cross-9 is made between two sepia individuals, but the progeny has 3:1 ratio of sepia and cream phenotypes. It is a complete dominance phenomenon. So, the genotype of both sepia parents should be heterozygous (sc) and the cross is as follows:

Therefore, the sepia is dominant over the cream.

The cross-10 is made between cream and albino individual, but the progeny has 1:1 ratio of cream and albino phenotypes. It is a complete dominance phenomenon (test cross). So, the genotype of the cream parent should be heterozygous (ca) and the albino parent should be (aa) and the cross is as follows:

Therefore, the cream is dominant over the albino.

Finally, genotypes that express the given phenotypes are as follows:

Therefore, order of dominance from all these crosses is as follows:

The genotypes of black individuals from the cross 7 and 8 are “bs” and “bc.” The cross between these two genotypes is as follows:

Therefore, the predicted progeny for possibility 1 and 2 is and the predicted progeny for possibility 3 is