| Date | May 2012 | Marks available | 1 | Reference code | 12M.1.HL.TZ1.33 |
| Level | Higher level | Paper | Paper 1 | Time zone | Time zone 1 |
| Command term | Deduce | Question number | 33 | Adapted from | N/A |
Question
Maize (Zea mays) contains 20 chromosomes in a diploid cell. How many chromosomes will be in each cell after the first and second division of meiosis?
Markscheme
A
Examiners report
Question 33 was the one that candidates found hardest on the whole paper, with fewer than 25% answering it correctly; below the expected level if candidates had all guessed the answer! The most popular choice was B, which was incorrect because it implies that the chromosome number is halved in the second division of meiosis not the first. The stage of meiosis in which the chromosome number is halved is not specified in any of the assessment statements, probably because it was thought to be obvious. The first division of meiosis is the reduction division. In humans for example, it results in the formation of two nuclei, each with 23 chromosomes consisting of two chromatids. The second division of meiosis results in four nuclei, each with 23 chromosomes consisting of a single chromatid.
