If a female sex-chromosome combination forms after fertilisation, which type of sperm caused it?
Answer and explanation
Correct answer: Sperm carrying an X chromosome
In the standard human system, the ovum always contributes one X chromosome because the mother is XX. A female chromosomal combination is XX, so the fertilising sperm must also contribute X: X from the ovum plus X from the sperm gives XX. A Y-bearing sperm would produce XY, while a sperm without a chromosome or both sperm together does not describe normal fertilisation. Therefore option A is correct.
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What is the correct answer to this question?
Sperm carrying an X chromosome
Why is this the correct answer?
In the standard human system, the ovum always contributes one X chromosome because the mother is XX. A female chromosomal combination is XX, so the fertilising sperm must also contribute X: X from the ovum plus X from the sperm gives XX. A Y-bearing sperm would produce XY, while a sperm without a chromosome or both sperm together does not describe normal fertilisation. Therefore option A is correct.
Which subject and chapter does this question cover?
This is a Class 10 Science question. Chapter: Heredity and Evolution. Topic: Sex determination.
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