PLEASE SHOW ALL WORK Two rough, black guinea pigs produce two offspring, one rou

Question

PLEASE SHOW ALL WORK

Two rough, black guinea pigs produce two offspring, one rough white and the other smooth black. If these same parents were to have additional offspring, what proportion of phenotypes would you expect? In Drosophila, gray body color is dominant over ebony, and straight wings are dominant over curved. A gray-bodied female with curved wings is mated with a gray-bodied male with straight wings, yielding some ebony, curved-wing offspring. What other types of offspring could be produced and in what proportions?

Explanation / Answer

3. In guinea pigs Black rough (RRBB) is dominant over smooth white (rrbb) .

In the above cross the parents are rough black but produce one rough white and one smooth black which means the parents are heterozygous as both the dominant and recessive characters are expressed.

So the parental genotype would be heterozygous RrBb .This is typical example for dihybrid cross inheritance The cross can be depicted as follows:

RrBb X RrBb

This can produce four different types of gametes RB,rB,Rb,rb

which when mate produce four different phenotypes rough black RRBBor RRBb,orRrBb,or rrbb

So the expected phenotypic ratio would be 9:3:3:1

9 rough black RRBB or RrBb

3 Rough white RRbb

3 smooth black rrBB or rrBb

1 smooth white rrbb

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