Answer:
Let attached earlobes allele be represented by a and free earlobe allele be represented by A.
Parent genotypes are Aa (heterozygous for free earlobes) and aa (homozygous recessive for attached earlobes, recessive traits occur in recessive pairs). Possible offspring genotypes are thus Aa and aa, given that the child inherits one allele from each parent. The probability of either genotype for the offspring is 50/50 hence the probability of the child having attached earlobes (aa) is 0.50.
