Question

A true breeding white squash (WWYY) is crossed with a true breeding green squash (wwyy) giving rise to a dihybrid offspring WwYy. Recall that W = white, w = color, Y = yellow, y = green. What color will the F1 offspring be? Consider the cross between two of the F1 offspring. Draw the chromosomes with the two genes if the genes are a) on the same chromosome or b) on different chromosomes. What would be the genotypes and the phenotypes of the F2 offspring if

a) the two genes are on the same chromosome (no crossing over), and
b) the two genes are on different chromosomes?

Answer 1

Parents (P1) Cross

WWYY (white, squash) X wwyy (green, squash)

(See attached punnet square)

All F1 progeny genotype will be heterozygous for both characters (WwYy) and will produce white squash phenotype because it is dominant color.

Cross Between F1 progeny

WwYy (white, squash) X WwYy (white, squash)

(See attached punnet square)

F2 Genotypic Ratios if Both Alleles Are on The Same Chromosome

1/16 will be homozygous dominant for both traits (WWYY)

2/16 will be homozygous dominant for White color and heterozygous for green color (WWYy)

1/16 will be homozygous dominant for White color and recessive for green color (WWyy)

1/16 will be homozygous recessive for White color and homozygous dominant for Green Color (wwYY)

2/16 will be homozygous recessive for white color and heterozygous for green color (wwYy)

1/16 will be homozygous recessive for both traits (wwyy)

This is a 1: 2: 1: 1: 2: 1 genotypic ratio if Both Alleles Are on The Same Chromosome

F2Genotypic Ratios if Both Alleles Are on The Different Chromosome

2/16 will be heterozygous for White color and homozygous dominant for green color (WwYY)

4/16 will be heterozygous for both traits (WwYy)

2/16 will be heterozygous for White color and homozygous recessive for green color (Wwyy)

This is a 2: 4: 2 genotypic Ratios if Both Alleles Are On The different Chromosome

Phenotypic ratios

9/16 will have dominant white color with recessive green color

3/16 will have recessive white with dominant green color

3/16 will have dominant green color with recessive white color

1/16 will have both receive combination of recessive traits

The phenotypic ratio will be 9:3:3:1.