IB Biology HL D1.1 DNA Replication Question Bank

Practise IB Biology HL D1.1 by explaining replication enzymes, strand directionality and applying DNA principles to PCR, electrophoresis and profiling.

Exam points

explain semi-conservative replication using strand separation, complementary base pairing and phosphodiester bonds
distinguish helicase breaking hydrogen bonds from DNA polymerase adding nucleotides to a growing strand
apply replication principles to PCR amplification, gel separation and interpretation of DNA profiles
trace leading and lagging strand synthesis using 5-to-3 directionality, RNA primers, DNA polymerases and ligase

Covered syllabus points

D1.1.1—DNA replication D1.1.2—Semi-conservative replication D1.1.3—Role of helicase and DNA polymerase D1.1.4—PCR and gel electrophoresis D1.1.5—Applications D1.1.6 (HL)—DNA polymerase directionality D1.1.7 (HL)—Leading vs. lagging strand D1.1.8 (HL)—Functions in replication D1.1.9 (HL)—DNA proofreading

[Maximum number: 8]

Angiospermophyta are vascular flowering plants.

Growth in living organisms includes replication of DNA. Explain DNA replication.

a. helicase unwinds the double helix

b. gyrase/topoisomerase relieves strains during uncoiling

c. helicase separates the two strands of DNA/breaks hydrogen bonds

d. each single strand acts as a template for a new strand / process is semi-conservative

e. DNA polymerase III can only add nucleotides to the end of an existing chain/to a primer

f. (DNA) primase adds RNA primer/short length of RNA nucleotides

g. DNA polymerase (III) adds nucleotides in a $5^{\prime}$ to 3 ' direction

h. complementary base pairing / adenine to thymine and cytosine to guanine

i. DNA polymerase (III) moves towards the replication fork on one strand and away from it on the other strand

j. continuous on the leading strand and discontinuous/fragments formed on the lagging strand

k. DNA polymerase I replaces primers/RNA with DNA

I. ligase joins the fragments together/seals the nicks

Marking guidance:

Accept unzips here but not for mark point a.

Do not accept letters.

8 max

[Maximum number: 3]

The confirmation of DNA as the genetic material, together with the elucidation of its structure by Crick and Watson, had a profound effect on modern biology.

Outline the reason that DNA replication is described as semi-conservative.

[Maximum number: 3]

(a)

Explain the role of the following enzymes in DNA replication.

[ 3 ]

(i)

Explain the role of helicase in DNA replication.

[ 1 ]

(ii)

Explain the role of DNA polymerase III in DNA replication.

[ 1 ]

DNA polymerase III: connects/forms (covalent) bonds between nucleotides in a $5^{\prime}$ to $3^{\prime}$ direction (OWTTE) / polymerizes nucleotides;

(iii)

Explain the role of RNA primase in DNA replication.

[ 1 ]

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Covered syllabus points

D1.1 DNA replication question 1

D1.1 DNA replication question 2

D1.1 DNA replication question 3

Question (a)

Question (i)

Question (ii)

Question (iii)