CIE iGCSE Co-Ordinated Science B16.1 Chromosomes and genes Exam Style Questions Paper 1
▶️ Answer/Explanation
Human sperm cells are produced in the testes and can carry either an X or a Y chromosome. Egg cells are produced in the ovaries and always carry an X chromosome. Therefore, row C correctly identifies sperm as the gamete that carries an X chromosome and is produced in the testes.
✅ Answer: (C)
✅ Answer: (C)
▶️ Answer/Explanation
Human body cells contain 23 pairs of chromosomes, one pair of which are the sex chromosomes.
Females have two X chromosomes (XX), while males have one X and one Y chromosome.
So the body cells of a human male contain the combination \(XY\).
✅ Answer: (B)
Females have two X chromosomes (XX), while males have one X and one Y chromosome.
So the body cells of a human male contain the combination \(XY\).
✅ Answer: (B)
▶️ Answer/Explanation
Sperm can carry either an X or a Y chromosome, while all eggs carry an X chromosome.
A male offspring \( (XY) \) results from an X-egg combining with a Y-sperm, while a female offspring \( (XX) \) results from an X-egg combining with an X-sperm.
Row B shows the correct sperm-egg combinations for each.
✅ Answer: (B)
A male offspring \( (XY) \) results from an X-egg combining with a Y-sperm, while a female offspring \( (XX) \) results from an X-egg combining with an X-sperm.
Row B shows the correct sperm-egg combinations for each.
✅ Answer: (B)
▶️ Answer/Explanation
Human sex is determined by one pair of chromosomes.
Males have one X chromosome and one Y chromosome (XY), while females have two X chromosomes (XX).
✅ Answer: (C)
Males have one X chromosome and one Y chromosome (XY), while females have two X chromosomes (XX).
✅ Answer: (C)
▶️ Answer/Explanation
Human females are XX and males are XY, so female gametes are always X and male gametes are X or Y.
A correct Punnett square crosses XX (female) with XY (male) to give offspring genotypes XX and XY in a 1:1 ratio.
The mark scheme confirms option C shows this arrangement correctly.
✅ Answer: (C)
A correct Punnett square crosses XX (female) with XY (male) to give offspring genotypes XX and XY in a 1:1 ratio.
The mark scheme confirms option C shows this arrangement correctly.
✅ Answer: (C)