IBBiologyHLTopic QuestionsContinuity & ChangeDNA Replication

Syllabus Edition

First teaching 2023

First exams 2025

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DNA Replication (HL IB Biology)

Topic Questions

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1
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The diagram shows the outcomes from four different models of DNA replication after one nuclear division. The parent DNA is shown in black and the newly synthesised DNA is shown in grey.

2-5easyq5

Which diagram represents semi-conservative DNA replication?

  • 1

  • 2

  • 3

  • 4

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21 mark

Which of the following correctly identifies the role of DNA polymerase in DNA replication?

  • Forms hydrogen bonds between the bases of the new nucleotides and the template strand.

  • Unwinds the DNA double helix at the replication fork.

  • Covalently bonds new DNA nucleotides together.

  • Joins up the Okazaki fragments on the lagging strand.

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31 mark

To which part of the DNA molecule will new nucleotides be covalently bonded during DNA replication?

7-1_q4

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41 mark

Which option correctly completes the sentence below?

In gel electrophoresis, DNA moves towards the _________.

  • Cathode

  • Negatively charged electrode

  • Anode

  • Tiny pores in the gel

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51 mark

Which of the following processes takes place in a thermal cycler?

  • Genetic modification

  • Polymerase chain reaction

  • Gel electrophoresis

  • Genetic fingerprinting

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61 mark

With reference to the DNA profile shown, which two individuals are the parents of child X?

e-3

  • 1 and 3

  • 1 and 2

  • 2 and 3

  • Individual 1 (only one parent is shown)

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1
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The following events occur in the process of DNA replication.

  1. Complementary strands are separated
  2. Free DNA nucleotides pair with complementary nucleotides on each template strand
  3. Hydrogen bonds are formed between complementary bases
  4. Hydrogen bonds are broken between complementary bases
  5. Covalent bonds form between the pentose sugar and the phosphate group of adjacent nucleotides

Which of the following is the correct order of the events?

  • 1 → 3 → 4 → 2 → 5

  • 3 → 1 → 2 → 4 → 5

  • 2 → 1 → 3 → 4 → 5

  • 4 → 1 → 2 → 3 → 5

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21 mark

Which of the following shows the appearance of the DNA strands that would result after two rounds of DNA replication? Note that the black strands represent DNA present in the original DNA molecule. The grey strands represent newly-synthesised DNA. 

diagram-10

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3
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A DNA profile was created for two genes in three individuals (A, B, and C).7-1_q2h

Which of the following statements, relating to the images provided, are correct?

I.

The relationship between DNA fragment length and distance moved through the gel is linear.

II.

Fragment length is determined by the number of repeated DNA sequences in a sample. .

III.

There is a percentage increase of 50 % between the distance moved by fragment Y and that moved by fragment X.

IV.
Individual A is homozygous for both of the genes tested.

  • I, II, and III only.

  • I, II, III, and IV.

  • II and IV only.

  • III and IV only.

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41 mark

Which row correctly identifies the enzymes in a replication fork?7-1_q3h

  I II III IV V
A. DNA primase DNA ligase DNA polymerase I Helicase DNA polymerase III
B DNA polymerase III DNA ligase DNA polymerase I Helicase DNA primase
C. DNA primase DNA ligase DNA primase DNA polymerase III DNA polymerase I
D. DNA polymerase I DNA polymerase III DNA ligase DNA gyrase DNA helicase

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51 mark

Some scientists were investigating the allele frequencies in a population of flies for a gene responsible for insecticide resistance.

They obtained DNA samples from a representative group in the population and then carried out PCR to amplify the DNA.

Scientists used the same restriction endonuclease on each sample before undertaking PCR, explain why.

  • To separate the DNA template strands

  • To isolate the required gene sequence

  • To produce smaller DNA fragments

  • To allow RNA polymerase to bind to the promotor region

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61 mark

DNA samples were taken from five individuals and analysed using gel electrophoresis to produce a DNA profile.  The DNA profile shows the results for a single gene.

What conclusions can be made from the profile shown in the image?

7KcF9rau_h-2

  • There are equal frequencies of two alleles

  • There are 3 different alleles for the gene

  • There are two alleles and the frequency of one allele is about 75%.

  • There are three homozygous individuals in the population

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11 mark

Which of the following statements about semi-conservative replication of DNA are correct? 

  1. DNA polymerase always works in the same direction along a strand of DNA, in the 3′ to 5′ direction.
  2. The action of DNA polymerase is followed by that of helicase.
  3. One strand of original DNA remains in each daughter molecule; the other strand has been made from free nucleotides.
  4. Crick and Watson proposed the hypothesis of semi-conservative replication, whereas experimental evidence was later provided by Meselson and Stahl.

  • I, III and IV

  • I and III

  • III and IV

  • I, II and IV

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21 mark

During the process of semi-conservative replication of DNA, which activity, relating to bonding, does not take place?.

  • Breaking of hydrogen bonds.

  • DNA polymerase forms an enzyme-substrate complex with free nucleotides. 

  • Formation of new covalent bonds between nucleotides.

  • Formation of new glycosidic bonds between deoxyribose molecules. 

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31 mark

The laboratory technique of Polymerase Chain Reaction (PCR) takes advantage of the ability of polymerase enzymes to copy pieces of genetic material quickly and accurately. Which of the following are necessary for successfully conducting PCR in a forensic examination at a crime scene? 

  1. An active sample of human DNA or RNA polymerase
  2. Buffer solution
  3. A sample of target DNA or RNA
  4. Free nucleotides
  5. Primer sequences

  • I, III, IV

  • II, III, IV and V

  • I, II, III and IV

  • All of them

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41 mark

When DNA polymerase adds a new nucleotide to a growing DNA strand, which part of the last nucleotide does it form a bond with?

  • Nitrogenous base

  • 5’ phosphate group of a pentose sugar

  • 1’ Carbon of a pentose sugar

  • 3’ -OH group of a pentose sugar

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51 mark

Okazaki fragments are short sections of DNA formed during DNA replication.

 Which of the following statements correctly describes why they form?

  • To help the DNA helix unwind

  • To enable replication of the leading strand

  • To act as a template for DNA polymerase 

  • To enable replication of the lagging strand

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61 mark

The shaded boxes in the diagram below (left) indicate DNA sequences called VNTRs from three different loci that were amplified (via PCR) from DNA found at a crime scene.

Each individual has a unique pattern of VNTRs in their genome. 

The diagram on the right shows DNA profiles of fragments amplified from the VNTR regions of four suspects.   q6a_7-1_dna_structure_replication_ib_hl_biology_mcq

Which of these suspects was most likely at the crime scene?

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71 mark

Which of the following statements explains the separation of molecules in electrophoresis?

  • DNA molecules from eukaryotes are broken up into smaller fragments.

  • Negatively charged proteins travel towards the anode.

  • Positively charged DNA molecules travel towards the cathode.

  • The larger the molecule, the further it travels through the gel.

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81 mark

What is the correct order of events for the stages of PCR shown in the diagram?

biology-3-4-med-ib-hl-q2

  1 2 3
A Annealing Elongation Denaturation
B Denaturation   Annealing Elongation
C Denaturation  Elongation Annealing
D Elongation Annealing Denaturation

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91 mark

If one molecule of DNA goes through 5 PCR cycles in the thermocycler, how many copies of that molecule of DNA will be produced?

  • 16

  • 6

  • 32

  • 64

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101 mark

What key feature of the genetic code makes it possible to transfer genes between species?

  • It has 2 strands.

  • It is universal.

  • The code is degenerate.

  • It can be amplified using PCR.

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111 mark

Which statement can not be concluded from the DNA profile shown?

biology-q5-3-4-med-ib-hl

  • Parent 1 and parent 2 are profiles of unrelated individuals.

  • Children 3 and 5 are non-identical twins.

  • Child 4 is related to parent 1 but not parent 2.

  • Child 6 is unrelated to any of the other individuals.

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