IBBiologyHLTopic QuestionsContinuity & ChangeGene Expression

Syllabus Edition

First teaching 2023

First exams 2025

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Gene Expression (HL IB Biology)

Topic Questions

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1
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Which of the following best describes the importance of regulating gene expression?

  • To ensure that essential genes are expressed all the time in the relevant cells

  • To ensure that only the relevant genes in the relevant cells are expressed at certain times

  • To ensure that only the relevant genes are expressed in the relevant cells at all times

  • To ensure that the same group of essential genes is expressed in all cells of the organism at certain times

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1
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Which of the following applies to both mutations and epigenetics?

  1. It may affect the visible characteristics of an organism
  2. The DNA base sequence can change and impact the expression of genes
  3. Environmental factors may play an important role in the development of changes
  4. Modifications may be passed on to the next generation at a cellular level
  5. The amino acid tails of histones are modified by methylation, acetylation and phosphorylation

  • I, IV and V.

  • I, III and IV.

  • II, III and IV.

  • I, III, IV and V.

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2
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Female embryos contain two copies of the X chromosome, even though they initially do not need both copies to be active. In order to avoid producing double the amount of polypeptides required, the paternal X chromosome is inactivated during the first few divisions after fertilisation. This is done by the methylation of lysine on different histones.

Which of the following provides the most accurate explanation of how this would inactivate the paternal X chromosome?

  • Adding a methyl group to lysine will maintain the negative charge to allow chromatin to become more condensed and inhibit transcription of the genes.

  • Adding a methyl group to lysine will maintain the positive charge to allow chromatin to become less condensed and inhibit transcription of the genes.

  • Adding a methyl group to lysine will maintain the positive charge to allow chromatin to become more condensed and promote transcription of the genes.

  • Adding a methyl group to lysine will maintain the positive charge to allow chromatin to become more condensed and inhibit the transcription of the genes.

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1
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Which of the following are examples of groups that could be added to the tails of histones to chemically modify them?

  1. Acetyl
  2. Hydroxyl
  3. Phosphate
  4. Amino

  • I. and III. only

  • II. and IV. only

  • I., II. and III.

  • II., III. and IV.

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21 mark

In humans, during periods of hypoxia (low oxygen in tissues) the transcription factor HIF (Hypoxia-Inducible Factor) binds to the Hypoxia Response Element (HRE) sequence and increases transcription of the EPO gene. This stimulates the production of red blood cells. The diagram shows the EPO gene and regulatory elements.                                                                                   q2_7-2_transcription_gene_expression_ib_biology_hl_mcq

Which kind of regulatory elements are HIF and HRE?

  HIF HRE
A

Activator protein

Enhancer sequence
B

Repressor protein

Silencer sequence
C

Enhancer sequence

Activator protein
D

General transcription factor

Enhancer sequence

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31 mark

The diagram below shows a nucleosome where the histone tails have had a methyl group added.

ib-methylation-of-histones

Which statement best describes the effect of methylation of histone tails?

  • Adding a methyl group causes the DNA to be less tightly wrapped

  • Adding a methyl group deactivates the gene

  • Adding a methyl group causes the DNA to be more tightly wrapped

  • Adding a methyl group helps maintain a positive charge

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41 mark

The simplified diagram below shows a section of DNA where a methyl (-CH3) group has been added to a cytosine base.q6_7-2_transcription_gene_expression_ib_biology_hl_mcq   

Which of the following best describes the outcome of direct methylation of DNA?

  • It stimulates the expression of the gene.

  • It prevents guanine from forming hydrogen bonds.

  • It inhibits the binding of transcription factors.

  • It causes breaks in the phosphate deoxyribose backbone.

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51 mark

Which of the following statements about DNA methylation are correct?

I.

DNA methylation varies throughout a lifetime.

II.

DNA methylation can be affected by environmental factors.

III.

Analysis of DNA methylation patterns can be used in the early detection of disease.

IV.

DNA methylation can cause changes in the DNA sequence.

  • I only

  • I and II

  • I, II and III

  • All the above

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