Question

Sex is determined by different factors in various species. However, in human beings, it is determined genetically. Which amongst the following option(s) is/are correct for human beings ?
Gamete carrying X chromosome from female parent.
Gamete carrying X chromosome from male parent.
Gamete carrying Y chromosome from male parent.

• A. (ii) and (iii)
• B. (i) only
• C. (i) and (iii)
• D. (iii) only

Hint:

In competitive exams, remember that "determination" implies choice or variation. Since the mother's contribution is fixed (always X), the father's contribution is the "determining" factor.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
In humans, sex is determined by the sex chromosomes. Females have two X chromosomes (\(XX\)) and males have one X and one Y chromosome (\(XY\)).
Step 2: Detailed Explanation:
During gamete formation:
- Females produce only one type of gamete (egg), which always carries an \(X\) chromosome. Therefore, statement (i) is a biological fact, but it does not "determine" the sex because there is no variation.
- Males produce two types of gametes (sperm): 50\% carry the \(X\) chromosome and 50\% carry the \(Y\) chromosome.
- If a sperm carrying an \(X\) chromosome fertilizes the egg, the child is female (\(XX\)).
- If a sperm carrying a \(Y\) chromosome fertilizes the egg, the child is male (\(XY\)).
Since the variation in the male gamete determines the outcome, options (ii) and (iii) are the factors that determine sex in human beings.
Step 3: Final Answer:
The sex of the child is determined by whether the sperm carries an X or a Y chromosome. Thus, (ii) and (iii) are correct.