CBSE 2025 · Region 2 · Set 1 · Q30 · 3 marks
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.
Figure 'X' Figure 'Y'(a)A man with attached earlobes marries a woman having free earlobes. $\displaystyle 50$% of their children have free earlobes and $\displaystyle 50$% 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.
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.
Figure 'X' Figure 'Y'
(a)
A man with attached earlobes marries a woman having free earlobes. $\displaystyle 50$% of their children have free earlobes and $\displaystyle 50$% 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.
Marking-scheme solution
(a)
Dominant trait - free earlobe: F f Recessive trait - Attached earlobe: ff.
Parents
$\displaystyle 50$% $\displaystyle 50$%
Progeny- Ff : ff
(b)
Gene combinations of:
Father - 'ff'
Mother - 'Ff'
HeredityMonohybrid and Dihybrid CrossesApplyshort_answermedium
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CBSE Class 10 Science past-paper question from the 2025board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.