Sex Determination (Brief) MCQs Quiz | Class 10
This quiz covers Sex Determination (Brief) for Class X Science (Code 086), part of Unit II: World of Living. It introduces the chromosomal basis of sex determination. Test your understanding with these multiple-choice questions. Submit your answers to see your score and download a detailed answer PDF for revision.
Understanding Sex Determination
Sex determination is a biological system that determines the development of sexual characteristics in an organism. In many species, including humans, this is genetically determined, primarily by specific chromosomes. This brief overview focuses on the chromosomal basis of sex determination in humans, a fundamental concept in genetics.
The Chromosomal Basis of Sex Determination in Humans
Human cells contain 23 pairs of chromosomes, totaling 46 chromosomes. These are divided into two categories:
- Autosomes: 22 pairs of chromosomes that carry genes for general body characteristics and are identical in males and females.
- Sex Chromosomes (Allosomes): The 1 pair of chromosomes that determine an individual’s sex.
Sex Chromosomes: X and Y
In humans, there are two types of sex chromosomes: X and Y.
- Females: Have two X chromosomes (XX).
- Males: Have one X chromosome and one Y chromosome (XY).
Inheritance of Sex Chromosomes
During reproduction, each parent contributes one sex chromosome to their offspring. This follows basic Mendelian inheritance principles:
- Female (XX): Produces only one type of egg cell, which always carries an X chromosome.
- Male (XY): Produces two types of sperm cells in roughly equal proportions:
- Sperm carrying an X chromosome.
- Sperm carrying a Y chromosome.
The sex of the child is determined at the moment of fertilization by the type of sperm that fertilizes the egg:
- If an X-carrying sperm fertilizes the egg (X), the resulting zygote will be XX (female).
- If a Y-carrying sperm fertilizes the egg (X), the resulting zygote will be XY (male).
Therefore, it is the father who determines the sex of the child because he produces both X and Y bearing sperm, whereas the mother always contributes an X chromosome.
Summary Table of Sex Determination
| Parent | Sex Chromosomes | Gametes Produced (Sex Chromosome) |
|---|---|---|
| Female | XX | X (all eggs) |
| Male | XY | X or Y (sperm, 50% each) |
Quick Revision Points
- Humans have 23 pairs of chromosomes (46 total).
- 22 pairs are autosomes; 1 pair are sex chromosomes (allosomes).
- Females have XX, males have XY.
- Eggs always carry an X chromosome.
- Sperm can carry either an X or a Y chromosome.
- The father’s sperm determines the sex of the child.
- An X sperm results in a female (XX).
- A Y sperm results in a male (XY).
Extra Practice Questions
- What are the two main types of chromosomes in humans?
- Which specific chromosome is responsible for determining male sex in humans?
- If a human egg is fertilized by a sperm carrying an X chromosome, what will be the genotype and sex of the offspring?
- Explain why the mother cannot determine the sex of the child.
- How many autosomes are present in a normal human diploid cell?
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