| Date | May 2012 | Marks available | 1 | Reference code | 12M.1.SL.TZ2.14 |
| Level | Standard level | Paper | Paper 1 | Time zone | Time zone 2 |
| Command term | State | Question number | 14 | Adapted from | N/A |
Question
Which is a feature of sex-linked genes in humans?
A. Males can only be heterozygous for the gene.
B. Females can only be homozygous for the gene.
C. Males can be either heterozygous or homozygous for the gene.
D. Females can be either heterozygous or homozygous for the gene.
Markscheme
D
Examiners report
Quite a few candidates picked option A instead of D, but this statement is invalid when dealing with sex-linked genes. The question had a high discrimination index.
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