Syllabus Edition

First teaching 2014

Last exams 2024

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DNA Structure & Replication (DP IB Biology: HL)

Exam Questions

3 hours35 questions
1a
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3 marks

The diagram below represents a nucleosome.

TzZbcTMf_hl-ib-e-7-1-q1a

Label parts A to C on the diagram.

1b
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1 mark

Prokaryotic DNA does not form nucleosomes.

State the reason for this.

1c
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2 marks

In eukaryotes, a great length of DNA is packed into a very small nucleus.

Describe how a nucleosome would contribute to make this possible.

1d
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1 mark

Rosalind Franklin and Maurice Wilkins used a specific technique to study the structure of DNA.

State the name of this technique.

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2a
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2 marks

The diagram below shows the process of DNA replication.

dna-replication-sq

Identify which strand of X and Y is the leading and lagging strand of the original DNA molecule.

2b
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1 mark

DNA replicates in a semi-conservative way.

Define the term 'semi-conservative' with regards to DNA replication.

2c
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2 marks

One of the enzymes involved with DNA replication is DNA primase.

Describe the role of DNA primase during DNA replication.

2d
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1 mark

DNA replication can only occur in the 5' to 3' direction in the new strand.

State the reason for this.

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3a
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1 mark

A crime was committed and the DNA profiles of the victim and a drop of blood found at the crime scene were constructed. These were compared to the DNA profiles of three possible suspects, as seen in the diagram below.

moMzkGAz_hl-ib-7-1-e-q3a

Identify the suspect that most likely committed the crime.

3b
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2 marks

Variable number tandem repeats (VNTRs) are short, non-coding regions of DNA that can be used in DNA profiling.

Explain the use of VNTRs in DNA profiling.

3c
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2 marks

The diagram below represents the structure of a chromosome.

dv29FFmY_hl-ib-7-1-e-q3c

Label parts R and S of the chromosome.

3d
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2 marks

R and S from the chromosome at part c) represents non-coding regions of DNA.

State the function of R and S in a chromosome.

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4a
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1 mark

The diagram below shows the experimental procedure followed by Alfred Hershey and Martha Chase.

jgqFjoK6_hershey-chase

State the aim of this experiment.

4b
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1 mark

Based on the information in the diagram at part a), state one reason why viruses were used in this experiment.

4c
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2 marks

Describe the events taking place between step 1 and 2 of the experiment.

4d
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2 marks

State the results obtained at the end of step 3.

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5a
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4 marks

One mark is available for clarity of communication throughout this question.

Describe the roles of non-coding regions of DNA molecules.

5b
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6 marks

The chain-termination method is one way in which DNA can be sequenced.

Outline the steps of the chain termination method of DNA sequencing.

5c
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5 marks

Molecular visualisation software is a useful tool with which to study the structure of molecules.

State five applications of molecular visualisation software in the fields of medicine and science.

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1a2 marks

Some DNA is associated with a protein called histone, which packages the DNA into structures called nucleosomes.

Describe the structure of a nucleosome. 

1b2 marks

State the functions of nucleosomes.

1c2 marks

Within the nucleus, DNA is replicated semi-conservatively in order to produce new cells. 

State two features of DNA and explain how these features are important in the process of semi-conservative replication of a cell’s DNA.

1d3 marks

The diagram below shows DNA replication.

q1d_7-1_dna_structure_replication_medium_ib_hl_biology_sq

Name the enzyme shown in the diagram and describe its function.

 

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2a2 marks

The diagram below illustrates a small section of a DNA molecule from the nucleus of a eukaryotic cell.

   q2a_7-1_dna_structure_replication_medium_ib_hl_biology_sqState the structures labelled X and Y.

2b2 marks

A repetitive sequence of DNA occurs at the ends of eukaryotic chromosomes, called a telomere.

Explain the role of a telomere. 

2c3 marks

Most of the DNA in an organism is contained within the nucleus. Some of this DNA is unique, whilst some is made up of highly repetitive sequences.

Contrast unique and highly repetitive sequences of DNA

2d3 marks

DNA was originally thought of as a protein. In the 1950s, Alfred Hershey and Martha Chase showed that DNA is a factor of heredity responsible for carrying genetic information from one generation to another.

Describe their experiment.

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3a3 marks

The sequence of DNA can be determined by a machine and technique developed by Frederick Sanger, called the dideoxyribonucleotide chain termination method.

Describe how nucleotides containing dideoxyribonucleic acid stop DNA replication.

3b1 mark

The chain termination process can be used to identify the sequence of base pairs.

q3b_7-1_dna_structure_replication_medium_ib_hl_biology_sq
   

Use the image above to identify the order of bases, starting with the smallest, in the block of DNA labelled X, on the right.

3c1 mark

Results from a paternity test using gel electrophoresis are shown in the image below. DNA was isolated from a mother, her child and two potential fathers. Primers designed to amplify different satellite DNA regions were used and amplified alleles are shown in the results below.

q3c_7-1-dna-structure--replication_ib_hl_biology

Use the gel electrophoresis DNA profiles in the image above to determine which male is the child's father.

3d2 marks

The DNA fragments separated in the gel electrophoresis in part (c) vary in size from 100 bp (base pairs) up to 5 000 bp. DNA fragments of known size were used to create the plot shown in the graph below.

q3d_7-1-dna-structure--replication_ib_hl_biology_sq

Use the line of best fit on the graph to determine the base pair length for DNA fragments that travelled 5 cm on the gel electrophoresis plate. Give answers to the nearest whole number.

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4a3 marks

DNA was studied by X-ray diffraction by Rosalin Franklin and Maurice Wilkins in the 1950’s.

Explain how X-ray diffraction allowed Franklin and Wilkins to view the molecular structure of DNA.

4b3 marks

Today, visualisation software can be utilised to analyse DNA in very high detail. The association between protein and DNA within the nucleosome can be seen.

Describe what may be visualised when analysing a nucleosome.

4c3 marks

Many visualisation techniques have been used to understand and study the structure of DNA. Watson and Crick used visualisation techniques, such as Franklin’s X-ray diffraction, to build a physical model of DNA. Their models were also influenced by the findings of other researchers, such as Erwin Chargaff.

Describe how the research findings of Franklin and Chargaff facilitated Watson and Crick to determine the structure of DNA.       

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5a6 marks

One mark is available for clarity of communication throughout this question. 

Outline the steps of DNA replication at a replication fork, describing the role of each of the enzymes involved.

5b4 marks

Rosalind Franklin’s X-ray diffraction helped to determine the double-helix structure of DNA.

Describe the deductions Franklin made from the images she produced by X-ray diffraction.

q5b_7-1_dna_structure_replication_medium_ib_hl_biology_sq
5c5 marks

Draw a labelled diagram to show four DNA nucleotides, each with a different base, linked together in two strands.

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1a
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2 marks

Arginine is an amino acid found in histone proteins and plays an important role in the interaction between histones and DNA within nucleosomes.

The diagram below shows the structure of arginine and a section of DNA within a nucleosome.

arginine-dna-bond-in-nucleosome-sqarginine-dna-bond-in-nucleosome-sq

Suggest how arginine facilitates the interaction between histones and DNA, by using the information in the diagram.

1b
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2 marks

Explain the role of nucleosomes in chromosome structure.

1c
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2 marks

Packing ratio is determined by dividing the length of DNA packed into a structure by the length of the structure.

Chromosome 11 consists of about 1.35 x 108 base pairs and the distance between adjacent base pairs is 3.4 nm. The chromosome is about 5 µm in length during metaphase.

Calculate the packing ratio of chromosome 11. Show your working.

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2a
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2 marks

A group of scientists studied the replication of DNA in Escherichia coli bacteria.

During their investigation, radioactive nucleotides were added to DNA that was actively replicating in a short pulse of about 5 seconds. This allowed the radioactive nucleotides to be incorporated into the new DNA strands. 

This was followed by a "chase" period, during which an abundance of unlabelled nucleotides was added to the DNA for different amounts of time, between 7 and 120 seconds. After the isolation and centrifugation of the DNA molecules, the results were obtained.

The graph below shows the results of their investigation.

size-of-dna-fragments-during-replication-graph-sq

Contrast the results obtained at a "chase" period of 7 seconds with those obtained at 120 seconds.

2b
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2 marks

Explain the results obtained at a "chase" period of 60 seconds.

2c
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1 mark

Suggest a possible explanation for the low number of small fragments present at 120 seconds.

2d
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2 marks

Sketch a line on the graph of the predicted results that could be obtained at a "chase" period of 150 seconds.

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3a
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2 marks

The following table shows the DNA base composition of different organisms. Note that for E. coli, the %C and %T has deliberately been left out.

Organism %A %C %T %G
Maize 26.7 23.3 27.0 23.0
Chicken 28.0 21.9 27.8 22.3
Octopus 33.0 17.2 32.1 17.7
Grasshopper 29.8 20.2 29.2 20.8
Sea urchin 32.6 16.9 33.1 17.4
Yeast 31.5 18.1 32.1 18.3
E. coli 24.7 - - X

State two deductions that can be made from the data.

3b
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2 marks

Calculate the possible value of X in the table in part a).

Show your working.

3c
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2 marks

The results from part a) are similar to those first obtained by Erwin Chargaff in the 1950s. 

Suggest how Chargaff's research may have impacted the work of Crick and Watson.

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4a
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1 mark

A mutation of the HTT gene may increase the risk of a person developing Huntington disease later in their lives. Blood samples from four different individuals were taken and the base sequences of a part of their HTT gene were sequenced using the chain termination method. These were compared to the normal base sequence of the HTT gene by reading from the smallest to the largest fragments.

The results from the gel electrophoresis are shown in the diagram below.

dna-sanger-sequencing-gel-sq

Identify the base sequence of the normal gene.

4b
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1 mark

Using the information in part a), deduce which patient(s) would have a higher risk of developing Huntington disease.

4c
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2 marks

During the chain termination method, modified nucleotides called dideoxynucleotides are used.

Contrast the structure and function of a dideoxynucleotide with a regular nucleotide.

4d
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1 mark

Suggest what would happen to DNA polymerase once a dideoxynucleotide is incorporated into the growing DNA strand.

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5a
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6 marks

One mark is available for clarity of communication throughout this question.

Compare and contrast DNA profiling with the chain termination method of DNA sequencing.

5b
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4 marks

The structure of DNA was discovered due to the research and input from several different scientists.

Outline how the discovery of the structure of DNA led to the development of the theory of semi-conservative DNA replication.

5c
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5 marks

Discuss the formation of Okazaki fragments during the process of replication on the lagging strand of a DNA molecule.

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