c. Coat colour in a breed of dog is controlled by a single gene. There are two possible versions (alleles) of this gene – black coat (B) and white coat (b). The gene for black coat is dominant to the gene for white coat.
In their cells, dogs contain two versions of the gene for coat colour.
Possible pairs are BB (black), Bb (black) and bb (white).
The table below illustrates a genetic cross between a male dog with genotype Bb and a female dog with genotype bb. The table is incomplete.
:Fig. 4.18 Parent genotype Sex cells produced Offspring genotype
Male dog Bb
B or b or
i. Complete the table by writing the two possible genotypes of the offspring that could result from this cross.
ii. What is the probability of the offspring having a black coat? Put a tick () in the correct box. 0%
25% 50% 75% 100%
iii. If a different male dog, with genotype BB, was bred with the same female dog, what would be the probability of their offspring having a black coat? Put a tick () in the correct box. 0%