Question

The breeding experiment using unknown genotype of grey and white mice, the following results were obtained.

If the grey female from cross IV were mated with the grey male from cross II, then which of the following would be true?

• A. All of the offspring would be grey.
• B. All of the offspring would be white.
• C. Half of the offspring would be grey.
• D. One-quarter of the offspring would be grey.
• E. One-quarter of the offspring would be white.

Answer 1

The correct option is A All of the offspring would be grey.

In the given table, cross III between white and white parent produce only white progeny which means that both white parents are homozygous here and the offspring is also pure breeding. Cross IV between grey and white parent produce only grey offspring showing the dominance of grey (G) allele over white (g). This cross also shows that parents are homozygous (GG and gg) here and the progeny is heterozygous dominant (Gg). Cross II between grey and grey parent produce both white and grey in almost 3 : 1 ratio which means that both parents are heterozygous dominant (Gg) in this cross. Out of total grey progeny of cross II, 2/3 will be heterozygous dominant (Gg) and 1/3 will be homozygous dominant (1/3).
Now the cross between grey females (Gg) from cross IV and grey male of cross II (GG or Gg) will produce all grey offspring.

Therefore, the correct answer is option A.