Question 21N.2.HL.TZ0.b
| Date | November 2021 | Marks available | [Maximum mark: 7] | Reference code | 21N.2.HL.TZ0.b |
| Level | HL | Paper | 2 | Time zone | TZ0 |
| Command term | Explain | Question number | b | Adapted from | N/A |
Explain transcription.
[7]
a. synthesis of RNA/mRNA / transcription of DNA to RNA;
b. RNA nucleotides linked together to form a strand/chain;
c. RNA strand assembled on DNA template/antisense strand / copy made of sense strand;
d. RNA polymerase carries out transcription/links RNA nucleotides;
e. uncoiling/separation of DNA strands;
f. 5’ end of nucleotides linked to 3’ end of (growing RNA) strand;
g. complementary base pairing (is the basis of copying the base sequence);
h. uracil instead of thymine in RNA;
i. starts at/RNA polymerase binds to a promoter;
j. regulated by transcription factors/DNA binding proteins/nucleosomes;
Annotated diagrams can be used.
Answers were mixed. Strong candidates had no difficulty in describing transcription in detail but weaker ones tended to get confused with replication and/or translation. Helicase was often stated as the enzyme that uncoils and splits the double helix, rather than RNA polymerase. Marks were not awarded merely for stating that transcription is 5’ to 3’ unless it was clear that the candidate understood that the 5’ terminal of a free nucleotide is linked to the 3’ terminal of the chain of nucleotides already linked up. Candidates are expected to show understanding in their answers, rather than just state memorized phrases.
