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ICSE Question Bank
2023Q1(i)Genetics – Some Basic Fundamentals
MCQModerate1 mark
1

Select the correct answer to the questions from the given options. (Do not copy the questions, write the correct answer only.)

The sex chromosome in a human ovum is:

Topic: Sex chromosome in the ovum

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Pick an option and check your answer. The full worked answer is below either way.

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Answer

Exam answer

(a) X chromosome.

Explanation

Every human ovum carries an X chromosome, and ONLY an X.

The reason: a woman is XX, so when meiosis halves her chromosome number, each ovum receives one X — there is no Y for her to give.

THE CONTRAST that the question is really testing: a man is XY, so half his sperms carry X and half carry Y. Option (d), "either X or Y", would be the correct answer for a SPERM, and it is placed here to catch anyone answering by reflex.

This is why the FATHER determines the sex of the child — the mother’s contribution is always X and cannot vary.

In words

X chromosome.

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