Question

a) What are sex chromosomes? Which sex chromosomes are found in male and female human beings? State the chromosomes responsible for the development of the male child in human beings.
b) Explain whether the traits like eye colour or height is genetically inherited or not. Do power lift and reading French also belong to the same category? Justify your answer.

Answer 1

Hint: Chromosomes are thread-like molecules that carry hereditary information that is passed from generation to generation such as eye colour, height etc. The nuclei of the cells in humans contain 22 pairs of autosomes and one pair of sex chromosomes. In females, the sex chromosomes pair has two X chromosomes and in males, it has one X-chromosome and one Y-chromosome.

Complete answer:
a)
- Sex chromosomes are the chromosomes that participate in sex determination.
- If there are two X chromosomes (XX), then it is a female and if there is one X-chromosome and one Y- chromosome (XY), it is a male.
- At the time of meiosis, in the male, the XY chromosome pair separates and passes either a X chromosome or a Y chromosome to separate gametes.
- This results in one-half of the sex gametes contain X chromosome whi;e the other half contains Y chromosome.
- All the female egg cells carry a single X chromosome.
- The eggs that are fertilized by X-bearing male gamete become female (XX) and those fertilized by Y-bearing male gamete become a male (XY).
- So, chromosome-Y is responsible for the development of male children in human beings.

b)
- Yes, traits like eye colour and height can be genetically inherited because these characters can be passed on from one generation to the next.
- But, in the case of power lifting and reading French, they are acquired characteristics which cannot be passed on from one generation to the next.

Note: Some babies are born with a single sex chromosome (45X or 45Y). This condition is referred to as sex monosomy.
- Some babies are born with three or more sex chromosomes (47XXX, 47XYY or 47XXY, etc.) and this is called sex polysomy.
- Due to the translocation of a small part of the sex determining region of the Y-chromosome, some males are born with 46XX chromosome.
- Due to mutations in the Y chromosome, some females are also born with 46XY chromosomes.