Page 62 - Biology - XII

directly transmitted from father to son, all aff ected females have an aff ected father and a carrier or
aff ected mother.

8. Traits transmitted from father to son are holandric traits transmitted by Y-chromosome, e.g. hair on
ear pinna.
9. X-chromosome (sex-linked) carrier genes of colour blindness, haemophilia, etc. Colour blindness
occurs in about 5–8 per cent of man and 0.5 per cent of woman.

SPOT - 1

Rolling of tongue
in ‘U’ tube like

Fig. 11.1: A Rolling of tongue

A. Comments on Pedigree (Fig. 11.1) of Rolling Tongue
1. The tongue-rolling ability is present in some (dominants) while in others it is absent (recessive).
Such individuals are called tongue-rollers and tongue non-rollers respectively.
2. The trait is represented by dominant gene (T–) and recessive genes (t, t).
3. It is not a sex-linked trait.

A Pedigree Chart of Rolling of Tongue
Male without trait

Parents Female without trait

Male with trait

Off spring Female with trait

Fig. 11.2

B. Comments on Pedigree (Fig. 11.2) (Father has the trait, mother does not have the trait)
1. It is the pedigree for rolling of tongue in human.
2. The male parent (father) have the characteristic of rolling of the tongue.
3. The female parent (mother) does not have the ability of rolling of the tongue.

4. Out of the four children (off spring) of the parents, the female off spring, the daughter is a tongue-
roller and all sons are tongue-non-rollers.
Parents

Off spring

Fig. 11.3
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