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.

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

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.