Question

Suppose two independently assorting genes are involved in the pathway that determines fruit color in squash. These genes interact with each other to produce the squash colors seen in the grocery store. At the first locus, the W allele codes for a dominant white phenotype, whereas the w allele codes for a colored squash. At the second locus, the allele Y codes for a dominant yellow phenotype, and the allele y codes for a recessive green phenotype. The phenotypes from the first locus will always mask the phenotype produced by the second locus if the dominant allele (W) is present at the first locus. This masking pattern is known as dominant epistasis. A dihybrid squash, Ww Yy, is selfed and produces 160 offspring. How many offspring are expected to have the white, yellow, and green phenotypes

Answer 1

Answer:

120 white individuals

30 yellow individuals

10 green individuals  

Explanation:

Available data:

• Dominant epistasis: Phenotypic frequencies 12:3:1

• W allele codes for a dominant white phenotype

• w allele codes for a colored squash

• Y allele codes for a dominant yellow phenotype

• y allele codes for a recessive green phenotype

• W allele will always mask the phenotype produced by Y or y alleles

• 160 offspring

Dihybrid Cross

Parental)   WwYy      x      WwYy

Gametes) WY   Wy    wY    wy

                 WY   Wy    wY    wy

Punnet Square)

                            WY         Wy        wY       wy

               WY     WWYY   WWYy   WwYY  WwYy

               Wy      WWYy   WWyy    WwYy  Wwyy

               wY      WwYY   WwYy    wwYY  wwYy

               wy       WwYy   Wwyy    wwYy  wwyy

F1 Phenotypic Frequency)

White phenotype: 12/16 = 120 individuals

Yellow phenotype: 3/16 = 30 individuals

Green Phenotype: 1/16 = 10 individuals

To know how many offspring are expected to have the white, yellow, and green phenotypes, you can perform a three simple rule. This is:

16 ------- 160 offspring

12 White ------- X = 120 offspring

3 Yellow ------- X= 30 offspring

1 Green --------X = 10 offspring