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How Sex Chromosomes Influence Traits
Every human has 46 chromosomes, or 23 pairs, inside almost every cell of the body. These
chromosomes carry DNA, which is like a giant instruction manual for how a person grows
and develops. One special pair of chromosomes is called the sex chromosomes. These
chromosomes help determine whether a person is male or female, but they also influence
other traits.
Sex chromosomes come in two types: X and Y. Females have XX, and males have XY. Each
parent gives one of these chromosomes to their child. Because mothers have two X
chromosomes, they can only pass on an X. Fathers, who have one X and one Y, can pass on
either an X or a Y. The combination of chromosomes decides the biological sex of the child:
XX for female or XY for male.
But sex chromosomes do more than that. The X chromosome carries many genes that affect
traits unrelated to being male or female—such as vision, blood clotting, and how certain
proteins are made. The Y chromosome has fewer genes, but some of them help control the
development of male characteristics.
Sometimes traits linked to the X chromosome show up differently in males and females. For
example, a male has only one X chromosome, so if that X has a certain gene variant, the trait
will appear. A female has two X chromosomes, so one X can sometimes ‘cover up’ a gene on
the other. This is why some X-linked traits are more common in males.
Understanding sex chromosomes helps scientists learn how traits are inherited and why
people have similarities and differences. Although chromosomes play a big role, they are
only part of what shapes who we are—environment, nutrition, and life experiences also
influence many traits.
Multiple Choice Questions
1. How many total chromosomes does a typical human have?
A. 12
B. 23
C. 46
D. 92
2. What do chromosomes carry that acts like an instruction manual?
A. Water
B. DNA
C. Minerals
D. Oxygen
3. What is the name of the special pair of chromosomes discussed in the passage?
A. Color chromosomes
B. Shape chromosomes
C. Sex chromosomes
D. Trait chromosomes
4. Which chromosome pairs do females have?
A. XY
B. YY
C. XX
D. XO
5. Which chromosome pairs do males have?
A. XX
B. XY
C. YY
D. XO
6. Which chromosome can the mother pass on to her child?
A. X only
B. Y only
C. X or Y
D. Neither
7. What determines whether the child will be biologically male or female?
A. The mother’s age
B. The father’s health
C. The combination of X and Y chromosomes
D. The environment
8. Why can X-linked traits show up more often in males?
A. Males have two X chromosomes
B. Males only have one X chromosome
C. Males have no X chromosomes
D. Males have more genes
9. Which of the following is a trait that can be influenced by genes on the X
chromosome?
A. Eye color
B. Blood clotting
C. Hair texture
D. Height
10. What other factors, besides chromosomes, help shape a person’s traits?
A. Environment, nutrition, and life experiences
B. Only the weather
C. Only exercise
D. Only school

All Answers 1

Answered by GPT-5 mini AI
1. C
2. B
3. C
4. C
5. B
6. A
7. C
8. B
9. B
10. A

Notes (brief): Q6 — mothers are XX so they can only pass an X. Q8 — males are XY, so a single X carries X-linked traits with no second X to mask them. Q9 — the passage specifically lists blood clotting as an X-linked trait example.