Epigenetic control of gene expression

Question 1

What has traditionally been accepted about DNA since the discovery of the double - helix model?

Answer 1

It has been traditionally accepted that DNA contains the instructions for making all parts of an organism

Question 2

How do genes and the environment interact to influence an organism’s phenotype?

Answer 2

Genes determine the features of an organism, but the environment can influence the expression of these genes, affecting the phenotype

Question 2

What recent discovery challenges the traditional view of DNA’s role in heredity?

Answer 2

It is now understood that DNA is only one part of heredity, and environmental factors can also influence gene expression without changing the DNA base sequence

Question 2

What was previously believed about environmental effects on phenotype and inheritance?

Answer 2

It was previously believed that environmental changes affecting the phenotype were not inherited by offspring

Question 3

What is epigenetics?

Answer 3

Epigenetics is the process by which environmental factors can subtly alter the gene function without altering the DNA base sequence of an organism’s offspring

Question 4

How is epigenetics contributing to the understanding of human diseases?

Answer 4

Epigenetics is helping to explain the causes of illnesses, such as diabetes and cancer, and may contribute to their cures

Question 4

What impact could epigenetics have on medicine?

Answer 4

Epigenetics could help in developing treatments or cures for diseases by understanding how environmental factors influence gene function and inheritance

Question 5

What is the epigenome?

Answer 5

The epigenome is a layer of chemical tags that cover DNA and histones, determining the shape of the DNA-histone complex and regulating gene activity

Question 6

How does the epigenome influence gene activity?

Answer 6

The epigenome keeps inactive genes tightly packed, preventing them from being read (known as epigenetic silencing), while unwrapping active genes so they can be transcribed

Question 7

What is epigenetic silencing?

Answer 7

Epigenetic silencing is when the epigenome tightly packs inactive genes in the DNA-histone complex, ensuring they remain switched off and cannot be read

Question 7

Is the DNA code flexible or fixed? What about the epigenome?

Answer 7

The DNA code is fixed, but the epigenome is flexible

Question 8

Why is the epigenome flexible?

Answer 8

The epigenome is flexible because the chemical tags respond to environmental changes. As a result factors, like diet and stress, cause chemical tags to adjust the wrapping/unwrapping of the DNA, so switching the genes on and off

Question 9

What is meant by the epigenome acting as a “cellular memory”?

Answer 9

The epigenome acts as a cellular memory because it reflects the accumulation of signals a cell received throughout its lifetime, shaping its gene activity

Question 10

How is the epigenome shaped during early development?

Answer 10

During early development, the epigenome is shaped by signals within the cells of the fetus and the nutrition provided by the mother

Question 11

How does the epigenome activate or inhibit genes?

Answer 11

The epigenome activates or inhibits specific sets of genes by adjusting the wrapping or unwrapping of DNA in response to environmental and internal signals

Question 11

How does an environmental signal initiate changes inside a cell?

Answer 11

The environmental signal stimulates proteins to carry its message inside the cell, passing it through a series of other proteins into the nucleus

Question 12

What happens once the environmental signal reaches the nucleus?

Answer 12

The message reaches a specific protein that attaches to a specific DNA sequence, causing changes that affect gene activity

Question 13

What are the two possible effects of the protein attaching to the DNA sequence?

Answer 13

1. It can change acetylation of histones, leading to activation/inhibition of genes
2. It can change methylation of DNA by attracting enzymes to add/remove methyl groups

Question 14

What is the acetylation of histones, how does it affect genes?

Answer 14

Acetylation of histones involves the addition of acetyl groups to histones, which can lead to the activation/inhibition of a gene by altering the DNA-histone complex

Question 14

What is DNA methylation, what role does it play in gene regulation?

Answer 14

DNA methylation involves adding or removing methyl groups to/from DNA. This process can either silence or activate specific genes by altering gene expression

Question 15

What role do enzymes play in DNA methylation?

Answer 15

Enzymes add or remove methyl groups during DNA methylation, influencing whether a gene is activated or inhibited

Question 16

What is the DNA-histone complex also known as?

Answer 16

The DNA-histone complex is also known as chromatin

Question 17

What happens when the DNA-histone complex is tightly packed?

Answer 17

When the DNA-histone complex is tightly packed, transcription factors cannot access the DNA, mRNA production cannot be initiated and the gene is switched off

Question 17

What happens when the DNA-histone complex is loosely packed?

Answer 17

When the DNA-histone complex is loosely packed, transcription factors can access the DNA, initiating mRNA production and switch the gene on

Question 18

How does the condensation of the DNA-histone complex affect transcription?

Answer 18

Condensation of the DNA-histone complex inhibits transcription by making the DNA inaccessible to transcription factors

Question 19

What two processes can lead to condensation of the DNA-histone complex?

Answer 19

1. Decreased acetylation of histones
2. Methylation of DNA

Question 20

How does decreased acetylation of histones affect the DNA-histone complex?

Answer 20

Decreased acetylation strengthens the association between DNA and histones, making the complex more condensed and inhibiting transcription

Question 21

How does DNA methylation inhibit transcription?

Answer 21

DNA methylation involves adding methyl groups to DNA, which enhance the condensation of the DNA-histone complex and prevents transcription factors from accessing the DNA

Question 22

What is acetylation?

Answer 22

Acetylation is the process of transferring an acetyl group to a molecule, often from acetyl coenzyme A

Question 22

What is deacetylation?

Answer 22

Deacetylation is the reverse of acetylation, where an acetyl group is removed from a molecule

Question 23

How does decreased acetylation of histones affect their charge?

Answer 23

Decreased acetylation increases the positive charges on histones

Question 24

How does the increased positive charge on histones affect their interaction with DNA?

Answer 24

Increased positive charges on histones strengthen their attraction to the negatively charged phosphate groups of DNA, resulting in tighter association

Question 25

What is the effect of decreased acetylation on the accessibility of DNA to transcription factors?

Answer 25

Decreased acetylation makes DNA less accessible to transcription factors, preventing them from initiating mRNA production

Question 25

What happens to a gene when acetylation of histones is decreased?

Answer 25

When acetylation of histones is decreased, the gene is switched off because the transcription factors cannot access the DNA to initiate transcription