Question 22N.2.SL.TZ0.4a

The majority of candidates managed to draw the correct symbol for a heterozygous female in the correct place in (a). However, there were a few who thought that X was male. Just over a half correctly gave 50$$% for (b). There were a large number of very pleasing answers in (c) to explain why the gene is not sex linked including that if it were sex linked, then you could not have a heterozygous male, and if it were sex linked, the daughter would have been heterozygous. The explanations in (d ) were not of such a high quality, with a large proportion failing to note that it hinges on the coding for a different amino acid, thus producing a different protein. Students should be careful about restating the stem as the 'protein changes' did not score as that was in the stem.