IB Biology HL D1.1 Dna Replication Questions

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 template strands, complementary pairing and one original plus one new strand
interpret Meselson–Stahl isotope-density patterns and contrast semi-conservative with conservative replication
distinguish helicase unwinding from DNA polymerase nucleotide addition
trace 5′ to 3′ synthesis and identify phosphodiester linkage formation
distinguish continuous leading-strand from discontinuous lagging-strand synthesis with Okazaki fragments and RNA primers
explain primase, DNA polymerase III, DNA polymerase I and ligase functions in replication
explain DNA polymerase III proofreading of mismatches and its effect on mutation rate
explain PCR amplification through denaturation, primer annealing and Taq-polymerase extension
interpret gel electrophoresis separation and DNA-analysis band evidence
analyse STR or DNA-profile patterns for paternity or forensic conclusions
outline medical applications of PCR including viral-strain identification, genetic testing, tissue typing or vaccine development

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
l. ligase joins the fragments together/seals the nicks

[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 ]

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

Question 1

Question 2

Question 3

Question (a)

Question (i)

Question (ii)

Question (iii)