Syllabus Edition

First teaching 2014

Last exams 2024

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Transcription & Translation (DP IB Biology: SL)

Exam Questions

3 hours35 questions
1a
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2 marks

The following diagram shows the process of protein synthesis.

Av~i7Cjw_e-1a

(i)

Identify stage X.

[1]

(ii)

State where in the cell stage X occurs.

[1]

1b
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2 marks

Label molecule A and B in the diagram.

1c
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1 mark

State one difference in structure between DNA and molecule A identified at part b).

1d
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1 mark

Molecule B is synthesised from monomers.

Identify the monomers of molecule B.

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2a
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2 marks

The diagram below shows one of the stages in protein synthesis.

e-2a

(i)

Identify the stage of protein synthesis represented by the diagram.

[1]

(ii)

State one reason for your answer in part i).

[1]

2b
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2 marks

Enzyme Y plays an important role during the stage of protein synthesis identified at part a) i).

(i)

Identify enzyme Y.

[1]

(ii)

State the role of this enzyme during protein synthesis.

[1]

2c
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2 marks

Label strands S and T of the DNA molecule.

2d
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2 marks

Explain the purpose of creating an mRNA copy of the genetic code on the DNA molecule.

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3a
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2 marks

The following DNA base triplets form part of a gene coding for a polypeptide.

         CCC  ATA  CTT  GGA

State the mRNA codons that would be transcribed from this section of the gene.

3b
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2 marks

The gene mentioned in part a) formed an mRNA molecule that consisted of 180 nucleotides.

Calculate the number of amino acids that will be coded for by this gene. Show your working.

3c
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2 marks

The table below shows mRNA codons and their corresponding amino acids.

mrna-codons-and-amino-acids-table

Use this table to state the amino acid sequence of the section of the gene given in part a).

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4a
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2 marks

The diagram below shows the structure of a ribosome.e-4a

Identify parts A and B of the ribosome.

4b
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1 mark

State one substance that a ribosome is composed of.

4c
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2 marks

Describe the role of a ribosome in the process of protein synthesis.

4d
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1 mark

The mRNA molecule that is shown in the diagram at part a) carries the genetic code in the form of codons.

Define the term 'codon'.

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5a
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3 marks

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

Describe how the structure of a tRNA molecule contributes to the accuracy of the translation.

5b
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5 marks

Draw a labelled diagram of two nucleotides bonded together within the same DNA strand.

5c
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7 marks

Outline the three stages of polymerase chain reaction (PCR).

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1a1 mark

Myoglobin is a eukaryotic protein consisting of a single polypeptide chain of 153 amino acids. 

Calculate the minimum number of DNA bases needed to code for Myoglobin.

1b3 marks

Haemoglobin is another eukaryotic protein; it contains both α and ꞵ polypeptide chains.
Some of the first seven amino acids of an α chain of haemoglobin, along with the corresponding bases in the sequence are shown below.  An mRNA codon and amino acid table is also provided.

Amino acid sequence Met (i) Leu (ii) (iii) Ala Asp
Base sequence in DNA antisense strand (3’➞5’) TAC CAC GAC AGA GGA CGG CTG

bilogy-2-6-q1b-ib-hl

Use the information provided to identify the missing amino acids from the sequence of seven shown above.

1c1 mark

A third eukaryotic protein, cytochrome c, is involved in the process of aerobic respiration. The diagram below shows part of the mRNA sequence and its corresponding amino acid sequence for cytochrome c in Mus musculus (house mouse) and Loxodonta africana (African elephant).

biology-2-6-q1c-ib-hl-sq

Identify the tRNA anticodon that corresponds to the amino acid serine (Ser).

1d2 marks

The triplet codes for the amino acid Ile in part (c) demonstrate a property of the genetic code known as degeneracy, or redundancy. 

Use the information in part (c) to:

(i)
Suggest what is meant when we say that the genetic code is degenerate/redundant.

(ii)

Identify one other amino acid that demonstrates this property.

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2a1 mark

Disease X is a genetic condition. It is caused by various mutations, one of which is shown in the diagram below.

biology-2-6-2a-sq-ib-hl

Identify the process marked Y in the diagram.

2b3 marks

The table below shows mRNA codons and their corresponding amino acids.

biology-2-6-2b-sq-ib-hl

Use the table above and your knowledge of protein synthesis to identify the contents of boxes (i)-(iii) in the diagram in part (a).

2c2 marks

Outline the role of transfer RNA in the process of protein synthesis.

2d2 marks

Explain why the protein produced as a result of the disease X mutation shown in part (a) does not function as it should.

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3a3 marks

The diagram below shows one cycle of the polymerase chain reaction (PCR). 


biology-2-6-sq-ib-hl

Outline the events that are taking place during stage 1 in the diagram.

3b1 mark

Molecule X in the diagram shown in part (a) is a DNA primer.

State the role of a DNA primer in PCR.

3c2 marks

Stage 3 in PCR involves an enzyme.

Explain how the enzyme is suitable for its role in PCR.

3d2 marks

State two applications of PCR.

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4a2 marks

The table below shows the exposed bases of two tRNA molecules involved in the synthesis of a protein.

Bases of tRNA anticodon UAU GAC
Bases of corresponding DNA antisense strand (i) (ii)


Identify the base sequences found on the corresponding sections of the DNA antisense strands.

4b3 marks

Outline how a gene codes for a polypeptide.

4c2 marks

A polypeptide is formed when a series of amino acids join to form a chain. 

Identify the following:

(i)

The chemical reaction that joins two amino acids together in a polypeptide. 

(ii)
The type of bond that joins two amino acids together in a polypeptide.

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5a5 marks

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

Draw an annotated diagram to illustrate the structure of a DNA double helix.

5b4 marks

Outline the advantages of producing insulin in bacteria.

5c6 marks

Describe the process of transcription in eukaryotic cells.

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1a1 mark

The sequence below shows the DNA bases coding for seven amino acids in the enzyme papain. Note that the sequence shown is from the sense strand.

            C  A  A  T  T  T  C  A  A  A  G  T  T  G  C  T  T  T  T  T  G

The image shows the genetic code (mRNA codons).

mrna-codons-and-amino-acids-table

Use the image to identify the sequence of amino acids in this part of the enzyme.

1b2 marks

Table 1 below shows some mRNA codons and the amino acids for which they code.

Table 1

Codon Amino Acid
ACG Threonine
UUA Leucine
CCA Proline
GUA Valine
GCU Alanine
AAU Asparagine

(i)

Identify the DNA sense strand sequence for leucine.

[1]

(ii)

Identify the amino acid carried by the tRNA with the anticodon CAU.

[1]

1c3 marks

Ricin is a protein produced by castor beans. In animal cells, ricin acts as an enzyme. This enzyme removes the adenine molecule from one of the nucleotides in the RNA that makes up the structure of ribosomes. As a result, the ribosome changes shape. Ricin causes the death of cells and is highly toxic to many animals.

Suggest how the effect of ricin on ribosomes could cause the death of cells.   

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2a2 marks

Transcription factors are proteins that influence the process of transcription. One mechanism by which transcription factors affect transcription is illustrated and described below.

1-7

      1. The transcription factor binds to region X at the start of a gene, also known as a promoter region.
      2. This causes enzyme Y to bind to the DNA.
      3. Transcription is initiated and enzyme Y moves along the DNA in the direction shown.
(i)

Identify enzyme Y.

[1]

(ii)

State the precise role of enzyme Y.

[1]

2b2 marks

As enzyme Y in part a) moves along the DNA, the base sequence on the template strand is as follows:

               A T G G C A A C T C T A 

Identify the tRNA anticodons that would bind with the mRNA produced from this section of DNA.

2c2 marks

The transcription factor shown in part a) is a protein.

Suggest, with a reason, how a mutation in the gene that codes for the transcription factor protein might affect the expression of the gene shown in part a).

2d2 marks

The transcription factor shown in part a) is an example of a type of transcription factor known as an activator. This means that it initiates transcription or increases the rate at which transcription takes place.

Use the illustration in part a) to suggest how a transcription factor might have the opposite effect and function as a repressor.

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3a2 marks

Scientists have modified the DNA of maize plants to enable them to resist attack by insects known as stem borers. The scientists transferred a gene from Bacillus thuringiensis (Bt), a soil bacterium, into the maize plants. The gene codes for proteins that are highly toxic to the stem borer insects. The toxic proteins bind to the cell-surface membranes of the insects, increasing the passage of ions through the membrane and into the insect cells.

Suggest how the Bt toxin causes the death of insect cells.

3b
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2 marks

A study was carried out to investigate which of several Bt toxin gene variants was most effective against three species of stem borer insect. The stem borers were allowed to feed on nine maize varieties (A–I), each modified with a different variant of the Bt toxin gene. The graph below shows the leaf area damaged by the stem borers after feeding on maize leaves for five days.

5-1

Calculate the percentage difference in leaf area damaged by Busseola fusca between the control and maize type H. 

3c3 marks

A farmer read the results of the study in part b) and concluded that they should buy maize variety B to achieve maximum resistance against stem borer damage in their maize crop.

Evaluate the farmer's conclusion.

3d3 marks

Another example of a genetically altered organism is the 'Flavr Savr' tomato. This tomato variety is genetically engineered to ripen and soften more slowly in order to increase its shelf-life.

The new gene is inserted into the tomato DNA alongside the normal gene that causes softening. The inserted gene prevents production of the softening enzyme beta polygalacturonase, which is coded for by the softening gene.

Parts of the base sequences for the mRNA produced during transcription of the softening gene and the inserted gene are shown below. 

Softening gene mRNA                 …AAUCGGAAU…

Inserted gene mRNA                   …UUAGCCUUA…

Suggest how the inserted gene reduces the production of the softening enzyme.

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4a
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2 marks

Until the development of genetic modification technology to produce human insulin on a large scale, diabetic patients had to use bovine-derived (from cattle) or porcine-derived (from pigs) insulin to help control their blood sugar levels. This insulin is extracted from the pancreas left over from animal slaughter in commercial abattoirs. 

Outline two drawbacks of using porcine-derived insulin for an insulin-dependent diabetic patient. 

4b
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2 marks

The ability to produce human insulin by using a genetically modified bacterium demonstrates the universality of the genetic code. 

Explain the meaning of the term, 'universality of the genetic code'.

4c2 marks

The strain of Escherichia coli (E. coli) used to produce human insulin has to be weakened in some way before it can be used to produce large quantities of insulin in industrial fermenters. This weakening step is only applicable to strains of E. coli designed for this process. 

Suggest why this weakened strain is required.  

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5a8 marks

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

Compare and contrast the processes of DNA replication and transcription.

5b6 marks

Explain the relationship between the genetic code and proteins.

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