Answer to Question #165247 in Molecular Biology for Aliya

Question

1.     A unique type of fox was discovered. It has a very shiny grey coat. In an attempt to figure out how this trait is inherited, a series of grey fox matings were analyzed. The resulting offspring were: 

 

75 grey foxes

39 white foxes

    37 black foxes

 

a)     What is the mode of inheritance of coat coloration among these foxes? Explain how you determined your answer. (2 marks)

 b)   Draw a Punnett square for these crosses (between grey foxes) and indicate the genotypic and phenotypic percentages of the offspring. (2 marks)

Not sure how to do punnett squares.

Please help me with this and walk me through how to do punnett squares

Answer 1

a) There is a recessive epistasis mode of inheritance of coat coloration among these foxes. This can be easily found from the number of individuals obtained: 75 grey, 39 white and 37 black.

As you can see that when cross is made between grey and grey then it will only be possible to get such number of individuals when there is genotype of grey is GgWg means here capital G and capital W both genes dominant alleles presence is require for Grey expression. And when cross is done between them then we can get 3 types of fox coloration with Grey, White and Black.

White will occur when both genes' recessive alleles are present or when one gene dominant allele- W dominant but g should be recessive.

Black coloration occur when only one gene that is B dominant allele is present.

Ans 2. We are going to cross grey * grey

Thus genotypes of Parents : GgWw * GgWw

Gamtes : GW Gw gW gw GW Gw gW gw

Now lets place the gametes of both the parents on either side of punnet square and make combinations:

These are the offsprings we get.

*Yellow marked: White foxes

*Black Bold is Black foxes

*Black italics are Grey foxes

Thus phenotypic ratio of Grey: Black: White = 9:3:4

or we can say phenotypic % of grey, black, white is 56.25%, 18.75%, 25% respectively

Genotypic Ratio is: GGWW: GGWw: GgWW: GgWw: GGww: Ggww: ggWW: ggWw: ggww

1:2:2:4:1:2:1:2:1

or in percentage: 6.25%, 12.25%, 12.25%, 25%, 6.25%, 12.25%, 6.25%, 12.25%, 6.25%