| Date | May 2012 | Marks available | 1 | Reference code | 12M.1.HL.TZ2.13 |
| Level | Higher level | Paper | Paper 1 | Time zone | Time zone 2 |
| Command term | State | Question number | 13 | Adapted from | N/A |
Question
Which is a source of chromosomes for pre-natal diagnosis of abnormalities by karyotyping?
A. Sperm
B. Ovaries
C. Erythrocytes
D. Chorionic villi
Markscheme
D
Examiners report
This was one of the best discriminators on the paper. 72% chose chorionic villi as the source of chromosomes for pre-natal diagnosis of abnormalities. The most popular wrong answer was erythrocytes, which was perhaps surprising as many of these candidates will have known that erythrocytes lack a nucleus.
