1 markWhich 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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Which of these features that affect gene expression are not passed directly from parent to offspring?
Promoters
Methyl groups
Enhancers
Transcription factors
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Why are monozygotic twin studies so useful for investigating the effects of the environment on gene expression?
Monozygotic twins are not genetically identical so they can be used to compare the difference in gene expression between two closely related individuals.
Monozygotic twins have the same DNA but inherit different epigenetic tags from each parent and this allows gene expression to be studied between the two.
Monozygotic twins can be compared to dizygotic twins and the results of these experiments can be used to determine the extent to which genetics or the environment are responsible for differences.
Monozygotic twins are studied to see if being exposed to the exact same environment causes the twins to develop the same epigenetic markers throughout their lives.
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1 markWhich of the following are examples of groups that could be added to the tails of histones to chemically modify them?
Acetyl
Hydroxyl
Phosphate
Amino
I. and III. only
II. and IV. only
I., II. and III.
II., III. and IV.
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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.
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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The diagram below shows a nucleosome where the histone tails have had a methyl group added.
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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The simplified diagram below shows a section of DNA where a methyl (-CH3) group has been added to a cytosine base.
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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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 patterns are always lost during meiosis. |
I only
I and II
I, II and III
All the above
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1 markWhich of the following applies to both mutations and epigenetics?
I. It may affect the visible characteristics of an organism
II. The DNA base sequence can change and impact the expression of genes
III. Environmental factors may play an important role in the development of changes
IV. Modifications may be passed on to the next generation at a cellular level
V. 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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1 markFemale 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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