Page 65 - Biology - XII

4. There is no method to fi nd whether the siblings are AA or Aa.
5. If parents are Aa and Aa, in the progeny the probability for occurrence of Aa in any child (free ear
lobe—a normal trait) is 2/3rd and occurrence of AA is 1/3rd.
6. If parent is a carrier (Aa), the off spring of generation II, i.e. 1 and 3 will have 1/2 chance or being Aa.

7. The off spring of generation II, 2 (daughter) and in generation III, 4 and 5 must be carriers. The
probability of (Aa) is 1.
SPOT - 4

A Pedigree chart of Widow's Peak

(i) Widow’s peak in male (ii) Straight hairline in male

(i) Widow’s peak in female (ii) Straight hairline in female
Fig. 11.10: (i) Widow’s peak (ii) Straight hairline

A. Observations (Fig. 11.10)
1. The trait of hairline on the forehead of a person can be V-shaped in the middle (widow's peak) or
without it (straight hairline).
2. The trait is represented by dominant gen (W, –) for the trait and (w, w) for recessive trait.
3. It is not a sex-linked trait.

Check yourself to fi nd the type of the hairline on your forehead. You can make your family pedigree
on widow’s peak trait.
A Pedigree Chart of Widow’s Peak

Parents Female with trait

Male with trait

Off spring

Fig. 11.11

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