Question 22N.2.SL.TZ0.4c
| Date | November 2022 | Marks available | [Maximum mark: 2] | Reference code | 22N.2.SL.TZ0.4c |
| Level | SL | Paper | 2 | Time zone | TZ0 |
| Command term | Explain | Question number | c | Adapted from | N/A |
Thrombophilia is a human genetic condition where the blood has an increased tendency to clot. The condition is caused by a single base substitution mutation in DNA. If a person is homozygous for the gene, they are at greater risk for developing a blood clot than an individual who is heterozygous. The pedigree chart shows the inheritance of thrombophilia in a family.
[Source: From The New England Journal of Medicine, Hopmeier, P. and Krugluger, W., n.d. Factor V Leiden and
Thrombophilia. [diagram online] Available at: https:// www.nejm.org/doi/full/10.1056/nejm199505183322014
[Accessed 2 November 2021], Vol. 332 No. 20. Page No. 1381. Copyright © 1995 Massachusetts Medical
Society. Reprinted with permission from Massachusetts Medical Society.]
Explain how the information in the box labelled B indicates that the gene is not sex-linked.
[2]
- if it was sex-linked it would be on the x chromosome;
- there cannot be a heterozygous male if the trait is sex-linked
- males would pass the allele to their daughter;
- daughter is not shown as heterozygous so it is not sex-linked;
