Question

Sex in human embryos is determined by:

• A. ‘X’ chromosome of egg
• B. ‘X’ or ‘Y’ chromosome of sperm
• C. Only ‘Y’ chromosome of sperm
• D. Health of mother

Answer 1

The Correct Option is B

In humans, the determination of an embryo's sex occurs at fertilization when the genetic material from the egg and sperm combine. The eggs produced by a female always contain an X chromosome. In contrast, a male's sperm can contain either an X or a Y chromosome. This means:

• If a sperm carrying an X chromosome fertilizes the egg, the resulting zygote will have two X chromosomes (XX), resulting in a female embryo.
• If a sperm carrying a Y chromosome fertilizes the egg, the zygote will have one X and one Y chromosome (XY), resulting in a male embryo.

Therefore, the sex of the human embryo is determined by whether the fertilizing sperm carries an X or a Y chromosome.

Answer 2

(1) ‘X’ chromosome of egg

This statement is incorrect. The sex of the human embryo is not determined solely by the ‘X’ chromosome of the egg. The egg always contributes an ‘X’ chromosome.

(2) ‘X’ or ‘Y’ chromosome of sperm

This statement is correct. The sex of the human embryo is determined by the sex chromosome contributed by the sperm. If the sperm carries an ‘X’ chromosome, the resulting zygote will be female (XX). If the sperm carries a ‘Y’ chromosome, the resulting zygote will be male (XY).

(3) Only ‘Y’ chromosome of sperm

This statement is incorrect. While the presence of a ‘Y’ chromosome in the sperm will result in a male embryo, the absence of a ‘Y’ chromosome (i.e., the presence of an ‘X’ chromosome) will result in a female embryo. Therefore, both ‘X’ and ‘Y’ chromosomes of the sperm are crucial.

(4) Health of mother

This statement is incorrect. The health of the mother does not determine the sex of the human embryo. The sex is determined by the sex chromosomes contributed by the parents.

Conclusion

The correct answer is (2) ‘X’ or ‘Y’ chromosome of sperm. The sex of the human embryo is determined by the sex chromosome contributed by the sperm.