Assertion: In humans, the gamete contributed by male determines whether the child produced will be male or female.
Reason: Sex in humans is polygenic trait depending upon a cumulative effect of some genes on X-chromosome and some on Y-chromosome. a) If both Assertion and Reason are true and the Reason is the correct explanation of the Assertion. b) If both Assertion and Reason are true and the Reason is not the correct explanation of the Assertion. c) If Assertion is true but the Reason is false. d) If both Assertion and Reason are false.

Options

A. If both Assertion & Reason are true and the reason is the correct explanation of the assertion, then mark a
B. lf both Assertion & Reason are true but the reason is no t the correct explanation of the assertion, then mark b
C. If Assertion is true statement but Reason is false, then mark c
D. If both Assertion and Reason are false statements, then mark d.

Answer

C

Explanation

In most animal species, chromosomes can be categorized as two types: autosomes and sex chromosomes. Autosomes are non-sex chromosoes that are the same number and kind between sexes. Sex chromosomes determine if the individual is male or female. Sex chromosomes in the human female are XX, those of the male are XY. Males produces X-containing and Y-containing gametes, therefore males determine the sex of offspring. Besides genes that determine sex, sex chromosomes carry many genes for traits unrelated to sex. X-linked gene is any gene located on X chromosome, used to describe genes on X chromosome that are missing on the Y chromosome.
When the female ovum is fertilized by the male, there is initiated an ineredibly complex chain of events which culminate nine months later in the birth of a child. During the very early stages of this gestation period the development of the embryo is predisposed in certain directions by the possession of the sex chromosomes which are composed of two elements, one contributed by the mother and the other by the father. The mother can contribute only what is termed as an X chromosome which predisposes towards the development of female structural, functional and temperamental characteristics, but the father can contribute either an X or a Y chromosome predisposing in the first instance to female, or in the second to male structural and functional and temperamental characteristics. In short, the sex of the child to be born is initially governed by the chromosomal contribution of the father. All chromosomes are paired, and the Y is dominant over the X chromosome when combined with it. A child conceived will therefore be subject during development therefore to a predisposition towards femaleness if receiving an X chromosome from the mother and an X chromosme from the father (XX), or towards maleness if receiving an X chromosome from the mother but a Y chromosome from the mother but a Y chromosome from the father (XY). Therefore sex in human is monogenic not polygenic. Polygenic traits or continuous traits are those traits that are determined by the combined effect of more than one pair of genes. An example of this is human stature. The combined size of all of the body parts from head to foot determines the height of an individual. There is an additive effect. The sizes of all of these body parts are, in turn, determined by numerous genes. Human skin, hair, and eye colour are also polygenic traits because they are influenced by more than one allele at different loci. The result is the perception of continuous gradation in the expression of these traits.