DP Biology (first assessment 2025)

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Question 22M.1A.SL.TZ1.14

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Date May 2022 Marks available [Maximum mark: 1] Reference code 22M.1A.SL.TZ1.14
Level SL Paper 1A Time zone TZ1
Command term Question number 14 Adapted from N/A
14.
[Maximum mark: 1]
22M.1A.SL.TZ1.14

Chromosome numbers vary between species. Which statement refers to humans?

A. An egg cell has 22 autosomes.

B. A sperm cell has 23 autosomes.

C. An egg cell has two X chromosomes.

D. A zygote has two autosomes.

[1]

Markscheme

A

Examiners report

This was another question that many candidates found too hard; less than 20 % answered correctly. The term autosome is included in sub-topic 3.2 of the program and an understanding of it was required in this question. That was not the only source of confusion though, as the most popular choice of answer - that a human egg cell has two X chromosomes — was clearly incorrect.

Syllabus sections