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4.Principles of Inheritance and Variation
normal
Excessive growth of hair on the pinna is a feature found only in males because
A
The female sex hormone oestrogen suppresses the character in females
B
The gene responsible for the character is present on the $Y-$chromosomes only
C
The gene responsible for the character is recessive in females and dominant only in males
D
The character is induced in males as males produce testosterone
Solution
Genes in the non-homologous region of $Y-$chromosome pass directly from male to male. In man, the $Y-$linked or holandric genes such as ichthyosis, hystrix, gravis hypertrichosis (excessive development of hairs on pinna of ear) are transmitted directly from father to son.
Standard 12
Biology
