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ICSE Question Bank
2020Q7(b)(v)Genetics – Some Basic Fundamentals
Short answerModerate1 mark
7(b)

The diagram given below is that of a developing human foetus. Answer the questions that follow: The diagram given below is that of a developing human foetus. Answer the questions that follow:

Figure for this question

Mention the sex chromosomes in a male and female embryo.

Topic: Sex chromosomes in the embryo

Previous-year question practice database

Answer

Exam answer

MALE embryo: XY FEMALE embryo: XX

Explanation

A human body cell has 46 chromosomes — 44 autosomes and 2 sex chromosomes (allosomes). It is the sex chromosomes that differ between the sexes.

THE CONSEQUENCE worth stating: since the mother is XX, every ovum carries an X. Since the father is XY, half his sperms carry X and half Y. So the SPERM decides the sex of the child: X sperm + X ovum = XX = GIRL Y sperm + X ovum = XY = BOY

Biologically, therefore, the FATHER determines the sex of the child and the chance is 50:50 at every conception — a point examiners raise deliberately, because women in India have often been wrongly blamed for it.

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