Problem

Solutions For An Introduction to Genetic Analysis Chapter 3 Problem 29P

Step-by-Step Solution

Solution 1

Step #1 of 4

The genes that determine stem color in tomatoes are as follows:

• Purple Stem = G

• Green stem = g

The genes that determine leaf shape in tomatoes are as follows:

• Cut = P

• Potato = p

The five mating’s of the tomato plants with the above phenotypes give following number of progeny.

Mating	Parental phenotypes	Number of progeny
		Purple and Cut	Purple and Potato	Green and Cut	Green and Potato
1	Purple and Cut × Green and Cut	323	102	309	106
2	Purple and Cut × Purple and Potato	220	206	65	72
3	Purple and Cut × Green and Cut	732	229	0	0
4	Purple and Cut × Green and Potato	405	0	389	0
5	Purple and Potato × Green and Potato	71	90	85	78

From the above data, all most all the mating’s have 1:1:1:1 ratio. So, these crosses may be either a test cross or a back cross.

If one can see the number of progeny form mating 1 and mating 2, the mating-1 shows that Cut (P) has more progeny than Potato (p). Thus, the P is dominant over p or P >p.

• The genotypes that express Cut (P) phenotype: PP and Pp

• The genotype that express Potato (p) phenotype: pp

The mating-2 shows that Purple (G) has more progeny than Green (g). Thus, the G is dominant over g or G >g.

• The genotypes that express Purple (G) phenotype: GG and Gg

• The genotypes that express Green (g) phenotype: gg

Step #2 of 4

The probable genotypes of parents of the each cross are as follows: Mating-1: It expresses an equal number of all phenotypes (Purple and Cut × Green and Cut).