The lowest part of the ear called earlobe, is closely attached to the side of the head in some of us (Figure…
The lowest part of the ear called earlobe, is closely attached to the side of the head in some of us (Figure 'X'), and not in others, called free earlobe (Figure 'Y'). Attached and free earlobes are two variants found in human populations. The gene for free earlobe is dominant over attached earlobes.
(a) A man with attached earlobes marries a woman having free earlobes. 50% of their children have free earlobes and 50% have attached earlobes. Explain the inheritance of this trait and write the trait combinations of the progeny.
(b) Write the gene combinations of the father and the mother in the above case.
Solution
(a) Dominant trait – free earlobe: Ff
Recessive trait – Attached earlobe: ff.
[cross diagram: Parents Woman-free earlobe (Ff) x Man-attached earlobe (ff); Gametes F, f x f, f; F1 Progeny Ff, Ff, ff, ff — free earlobe : attached earlobe]
50% 50%
Progeny- Ff : ff
(Award marks if answer is written in explanation form)
(b) Gene combinations of:
Father – 'ff'
Mother – 'Ff'
(award marks if any other letter denoting the trait is used)
