Question

Match the following –

List I	List II
a. White forelock	i. X-linked chromosome
b. Beard in man	ii. Y-linked chromosome
c. Bobbed bristles in Drosophila	iii. Sex-limited character
d. Follicular hyperkeratosis	iv. Sex- influenced character
v. XY-linked character

Answer 1

Sex-influenced characters are the characters that are influenced by sex. Sex limited characters are the characters that are limited to only one sex of a population. In addition, females have XX chromosomes and males have XY chromosomes. Follicular hyperkeratosis is a disorder in females only.

Complete answer: Let us look at all the options of list I, one by one, and then choose the correct alternatives for them from list II.
-White forelock: White forelock is a sex-influenced character. Sex influenced character means that the phenotypes are sex-specific for the same genotype in males and females. Sex-influenced traits are autosomal traits. Here the sex of the individual determines the dominance of the gene governed.
Therefore, white forelock matches with the sex-influenced character of option IV.
-Beard in man: The beard in human males is a sex-limited character. This is due to the androgenic hormones. The androgenic hormones cause the expression of the governing dominant gene. In the case of human females, androgenic hormones never attain the required levels. Due to this, these genes are never expressed in females and they do not possess beards like men. Therefore, the beard of the man matches with the sex-limited character of option III.
-Bobbed bristles in Drosophila : The bobbed bristles in Drosophila are an XY-linked character. The bobbed bristles in Drosophila are because of a gene that is present on that part of the Y chromosome which is homozygous with the X chromosome. This homozygous part of the Y-chromosome synapses with the X-chromosome. Therefore, it is known as an XY-linked character. Therefore, bobbed bristles in the Drosophila match with the XY-linked character of option V.
Follicular hyperkeratosis: Follicular hyperkeratosis is caused due to a gene present on the X chromosome. This gene is inheritable in an X-linked dominant manner. Therefore, follicular hyperkeratosis matches with the X-linked chromosome of option I.
Hence, the correct answer is option (B).
Note: Sex-limited traits and sex-influenced traits are different from each other. The genes of sex-limited traits are autosomal and are found in both the sexes but express themselves in one sex only. For example – milk glands in females, deep voice in males, etc. Sex-influenced traits are those autosomal genes that are influenced by the sex of the bearer. These traits appear more frequently in one sex than another. For example – pattern baldness, short index finger in males, etc.