Which diagram shows the sex chromosomes when a sperm fertilises an egg to produce a baby girl?

The correct option is A

The correct option is A:

Explanation of the correct option:

1. Sex chromosomes present in the gametes determine the sex of the individual.
2. Humans have two sex chromosomes - X and Y chromosomes.
3. Human females are homogametic in nature i.e., they have two copies of the X chromosome while males are heterogametic in nature with one copy of each of the X and Y chromosomes.
4. So, when a sperm with X chromosomes fertilizes the egg with X chromosomes, the resultant zygote will be XX (homogametic) and will produce a baby girl.

Explanation of the incorrect option:

Option B:

1. Human females are homogametic and they contain two copies of the X chromosome.
2. They do not have the Y chromosome, so they cannot produce gametes with the Y chromosome.

Option C:

1. Human males are heterogametic i.e., they have one X and one Y chromosome.
2. When a sperm with Y chromosomes fertilizes the egg with X chromosomes, the resultant zygote will be XY (heterogametic) and will produce a baby boy.

Option D:

1. Human females are homogametic with two copies of the X chromosome.
2. They cannot produce gametes containing Y chromosomes.

Final answer: Diagram A shows the sex chromosomes when a sperm fertilizes an egg to produce a baby girl.