An experiment was carried out to investigate a gene for coat colour in mice. The diagram shows the results of three crosses between different mice, producing three different families, P, Q and R. What is the maximum possible number of heterozygous mice shown in the diagram?

Answer:

25) H

In family P, a grey mouse was mated with a white mouse. Since all 4 offsprings were grey, we can conclude that the white coat must be recessive.

Therefore, all of the grey mice can be heterozygous. Since there are 12 mice in the diagram, all of them could potentially be heterozygous.

Hence the answer is H.