Question 19M.2.HL.TZ2.2b.i
| Date | May 2019 | Marks available | [Maximum mark: 2] | Reference code | 19M.2.HL.TZ2.2b.i |
| Level | HL | Paper | 2 | Time zone | TZ2 |
| Command term | Outline | Question number | b.i | Adapted from | N/A |
DNA methylation has a critical role in gene regulation by affecting transcription. Samples were taken from two colon cancer tumours (T1 and T2) and two normal colon samples (N1 and N2). A particular gene was implicated as a possible cause of cancer. The promoter of this gene was cloned (A–J). The data show the DNA methylation patterns from these samples. The numbers (32–269) represent different markers in the promoter.
[Source: Philipp Schatz, Dimo Dietrich & Matthias Schuster. Rapid analysis of CpG methylation patterns using RNase T1
cleavage and MALDI-TOF. Nucleic Acids Research (2004) 32 (21): e167, doi:10.1093/nar/gnh165.
Reproduced by permission of Oxford University Press]
Outline the difference in methylation pattern between tumorous and normal tissue samples.
[2]
a. «overall» much more methylation in the colon tumour samples than normal ✔
b. tumour and normal samples the markers 258 and 269 similar degree of methylation/fewer differences ✔
c. degree of methylation on certain markers may correlate with the presence of cancer / correct example of a marker only methylated in tumour cells eg marker 32 ✔
Many students detected that greater degrees of methylation in tumour samples. Fewer could accurately summarize the specific differences between methylation in the two samples.
