Question 21M.2.HL.TZ2.c
| Date | May 2021 | Marks available | [Maximum mark: 7] | Reference code | 21M.2.HL.TZ2.c |
| Level | HL | Paper | 2 | Time zone | TZ2 |
| Command term | Explain | Question number | c | Adapted from | N/A |
Insulin is produced in β cells of the pancreas and not in other cells of the human body. Explain how differentiation of cells and regulation of gene expression allow proteins such as insulin to be produced in only certain types of body cell.
[7]
a. insulin production is determined by a gene ✔
b. gene for insulin (is found in all cells), but only activated in (β cells of) pancreas ✔
c. stem cells differentiate into specialized cells/(into pancreatic β) ✔
d. during differentiation some genes are turned on and others off ✔
e. insulin is a hormone that regulates the amount of glucose/sugar in blood ✔
f. pancreatic β cells have sensors that detect glucose level in blood ✔
g. an increase in glucose will increase transcription of mRNA of insulin ✔
h. the site of transcription of insulin is in the pancreatic β cells ✔
i. gene transcription is regulated by proteins that bind to specific base sequence in DNA/ enhancers/silencers/promoter proximal elements ✔
j. regulatory sequences/proteins are specific to the gene they regulate / insulin regulator proteins are only found in in the pancreatic β cells ✔
k. (DNA) methylation (usually) inhibits gene expression / (histone) acetylation promotes gene expression / tightness of coiling of DNA around histones affects gene expression ✔
Accept sugar as equivalent to glucose.
In general, scores for this question were quite low. Candidates were too vague in their answers. Many failed to discuss chemical modification of DNA and the role of non-coding sequences in the regulation of gene expression.
