Question

When a human egg is fertilized by a sperm having ‘Y’ chromosome, the zygote has the following combination of chromosomes:

• A. 44 + XX
• B. 22 + XX
• C. 44 + XY
• D. 22 + XY

Hint:

Egg always gives X. X sperm → XX (Female), Y sperm → XY (Male).

Answer 1

The Correct Option is C

To solve this question, we need to understand the basic concepts of human genetics, particularly the chromosomal composition resulting from fertilization.

Humans have 46 chromosomes in total, which are arranged in 23 pairs. Among these pairs, 22 pairs are autosomes, and the remaining one pair is the sex chromosomes, which determine the sex of an individual. Typically, females have two X chromosomes (XX), and males have one X and one Y chromosome (XY). Here is the step-by-step solution:

1. Each parent contributes one chromosome to each pair. Therefore, a mother can only contribute an X chromosome to the offspring, while a father can contribute either an X or a Y chromosome.
2. If a human egg (which contains 22 autosomes + X chromosome) is fertilized by a sperm that contains 22 autosomes + Y chromosome, the resulting zygote will have the following chromosome configuration: 44 + XY.

The 'XY' signifies that the child will be genetically male. Now, let's analyze the given options:

• 44 + XX: This configuration would occur if the sperm carried an X chromosome, resulting in a female zygote.
• 22 + XX: This configuration is incorrect because it does not account for the full complement of chromosomes.
• 44 + XY: This is the correct configuration for a male zygote resulting from the fertilization of an egg by a Y-carrying sperm.
• 22 + XY: This configuration is incorrect because it only includes half of the total chromosomal content.

Therefore, the correct answer is the option 44 + XY.