Question

In the late 1920s a mutation occured in many silver fox farms around the world. these farms that sold expensive furs were proud of the quality of their furs , and each advertised that it had the best, most pure breed of all the fox farms. The new mutations produced a "platinum" coat pattern that was commercially desirable, so the farms crossed them to get more. The results of their breeding experiments were as follows: (1) silver - silver ® all silver offspring; (2) silver - platinum ® equal numbers of silver and platinum; (3) platinum - platinum ® 2 platinum for each silver offspring. Explain.

Answer 1

In a homozygous state, the allele "P" is lethal. Those individuals with PP genotype will be born dead.

Step-by-step explanation:

The allele P is dominant over p and expresses the trait "platinum". But in the homozygous state, it is mortal, PP. The allele p expresses the "Silver" trait.

This is:

• For platinum individuals, the genotype should be Pp

• For silver individuals, the genotype should be pp

• For dead individuals, the genotype should be PP.

So in the crosses, the punnet squares are:

1- Silver x Silver

Parental) pp x pp

Gametes) p p p p

Punnet square)

p p

p pp pp

p pp pp

F1 Genotype) 100 % recessive homozygote pp

2- Silver x Platinum

Parental) pp x Pp

Gametes) p p P p

Punnet square)

p p

P Pp Pp

p pp pp

F1 Genotype) 50 % recessive homozygote pp,

50% heterozygote for the trait Pp

3- Platinum x Platinum

Parental) Pp x Pp

Gametes) P p P p

Punnet square)

P p

P PP Pp

p Pp pp

F1 Genotype) 25 % recessive homozygote pp

50% heterozygote for the trait Pp

25% dominant homozygote PP. This is a dead

individual.

In this last cross, individuals with genotype PP dye, so, of the whole offspring, there are two platinum for each silver offspring.