DP Biology (first assessment 2025)

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Question 23M.2.HL.TZ1.b

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Date May 2023 Marks available [Maximum mark: 7] Reference code 23M.2.HL.TZ1.b
Level HL Paper 2 Time zone TZ1
Command term Describe Question number b Adapted from N/A
b.
[Maximum mark: 7]
23M.2.HL.TZ1.b

Describe the processes that are carried out by enzymes that bind to DNA.

[7]

Markscheme

replication

a. helicase unwinds the double helix/DNA;
b. helicase breaks hydrogen bonds between/separates/unzips DNA strands;
c. (DNA) gyrase/topoisomerase releases tensions in DNA as it unwinds;
d. (DNA) primase adds RNA primers (where DNA polymerase can bind);
e. DNA polymerase (III) replicates DNA/adds nucleotides (to make new strand);
f. DNA polymerase I replaces RNA (primers) with DNA;
g. DNA ligase seals nicks/joins sugar-phosphate backbones/joins (Okazaki)fragments;

transcription

h. RNA polymerase used for transcription;
i. RNA polymerase unwinds / separates DNA strands / binds to the promoter;
j. RNA polymerase copies DNA base sequence of a gene/makes mRNA;
k. restriction enzymes/endonucleases cut DNA at specific base sequences;
l. telomerase adds nucleotides to the ends of chromosomes/makes telomeres;

Syllabus sections