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Q22 (NDA-I/2013) Science & Technology › Basic Science (Physics, Chemistry, Biology) › Genetics and evolution Answer Verified

The sex of a newborn baby is determined by the chromosome inherited from

Result
Your answer: —  Â·  Correct: B
Explanation

In humans, the sex of a newborn is determined by the sex chromosomes inherited from the parents. Females possess two X chromosomes (XX), meaning all eggs they produce carry an X chromosome [1]. Males possess one X and one Y chromosome (XY), resulting in two types of sperm: 50% carrying an X chromosome and 50% carrying a Y chromosome [1]. Since the mother always contributes an X chromosome, the sex of the child depends entirely on whether the father's sperm contributes an X or a Y chromosome [2]. If the sperm carries an X chromosome, the resulting XX combination produces a girl; if it carries a Y chromosome, the XY combination produces a boy [1]. Thus, the paternal chromosome is the deciding factor in sex determination [2].

Sources

  1. [1] Science , class X (NCERT 2025 ed.) > Chapter 8: Heredity > 8.2.4 Sex Determination > p. 132
  2. [2] Science , class X (NCERT 2025 ed.) > Chapter 8: Heredity > What you have learnt > p. 133
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SIMILAR QUESTIONS

CDS-II · 2020 · Q109 Relevance score: 3.70

ln human beings, the chromosomes that determine birth of a normal female child are ________.

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Assertion (A) : In human beings, the females play a major role in determining the sex of the offspring. Reason (R) : Women have two- ‘X’ chromosomes.

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In a family, the age of father, mother, son and grandson are A, B, C and D respectively. Given that A - B = 3, B + C = 78, C + D = 33 and the average age of the family is 34 years, then B - C is :

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If B’s mother is A’s mother’s daughter, how is A related to B ?

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In the context of hereditary diseases, consider the following statements : 1. Passing on mitochondrial diseases from parent to child can be prevented by mitochondrial replacement therapy either before or after in vitro fertilization of egg. 2. A child inherits mitochondrial diseases entirely from mother and not from father. Which of the statements given above is/are correct?