Epigenetics

Question 1

What are epigenetics?

Answer 1

Any process that alters gene activity/expression without changing DNA sequence

Question 2

What is the difference between genetics and epigenetics?

Answer 2

Genetic inheritance involves passing down DNA sequences (genes) from parents to offspring, determining traits through fixed genetic code.

Epigenetic inheritance involves changes in gene expression without altering the DNA sequence, influenced by environmental factors and reversible modifications like DNA methylation or histone modifications.

Question 3

What are the two processes of epigenetics?

Answer 3

Methylation and DNA packaging

Question 4

What is methylation?

Answer 4

The addition of CH4 (methane) to DNA

Question 5

What kind of methylation can silence genes?

Answer 5

Hyper-methylation

Question 6

What is DNA packaging?

Answer 6

DNA packaging is the process of condensing DNA to fit inside the nucleus. It involves:
Histones – Proteins that DNA wraps around, forming nucleosomes.
Chromatin – DNA + histones, organized as euchromatin (loose, active) or heterochromatin (tight, inactive).
Chromosomes – Fully condensed DNA structures during cell division.

Question 7

What is heterochromatin?

Answer 7

Tightly-packed DNA. Gene can be hidden/silenced & inaccessible to transcription machinery

Question 8

What is euchromatin?

Answer 8

Loosely-packed DNA, allows gene expression

Question 9

What do the epigenetic modifications (methylation and DNA packaging) have in common?

Answer 9

They are both reversible and heritable

Question 10

What do heterochromatin and euchromatin have in common?

Answer 10

Both are present in a non-dividing nucleus and DNA can switch between both

Question 11

What is X-inactivation? How does it count as an epigenetic modification?

Answer 11

It silences one X chromosome in each somatic cell in all females. In early development, X in each cell is randomly inactivated. Chromosomes become tightly condensed (Barr body: inactive X.) The same X will be inactivated in each daughter cell.

Question 12

What are Barr bodies?

Answer 12

Inactivated X chromosomes in female cells, ensuring dosage compensation between males (XY) and females (XX). Importance: gene balance, epigenetic regulation, sex chromosome disorder identification

Question 13

When do Barr bodies form?

Answer 13

Early embryonic development

Question 14

What is anhidrotic dysplasia?

Answer 14

when the gene needed for the development of sweat glands is on X chromosome. Males: no sweat glands, Females: both

Question 15

What is Turner syndrome?

Answer 15

when females have one X chromosome (XO) because some genes are needed in a double dose (45,X) instead of (46,XX). result of nondisjunction in formation of sperm or egg

Question 16

How can an individual with a monosomy survive through adulthood when autosomal monosomies are lethal?

Answer 16

An individual with Turner syndrome (45,X) survives because the X chromosome is different from autosomes. (sex chromosome)
The X chromosome carries fewer vital genes compared to autosomes. Autosomal monosomies are lethal because they remove essential genes needed for survival.

Question 17

What happened when agouti mice were treated with DNA methylating agents?

Answer 17

Gene Silencing – The Agouti gene is turned off, preventing excessive yellow fur and obesity.
Healthier Offspring – Pups are more likely to have brown fur, normal weight, and lower disease risk.
Epigenetic Inheritance – These methylation patterns can persist through generations, influencing offspring traits without changing DNA sequences.

Question 18

What is an operon?

Answer 18

A group of genes that is transcribed together into a single mRNA molecule. Regulation of operons involves negative control of genes (turning them off).

Question 19

What is a repressible operon?

Answer 19

an operon where transcription is usually on but can be inhibited (repressed) when a specific molecule binds to a regulatory protein

Question 20

What is an inducible operon?

Answer 20

an operon that is usually off but can be stimulated to be on

Question 21

what are inducible enzymes?

Answer 21

enzymes where synthesis is induced by a chemical signal

Question 22

what are repressible enzymes?

Answer 22

enzymes which function in anabolic pathways

Question 23

what is an activator in gene expression?

Answer 23

a protein that binds to DNA and stimulates the transcription of a gene

Question 24

what is an epigenome?

Answer 24

The body’s complex chemical network that controls gene expression. Everyone has a unique, changeable epigenome.

Question 25

What is a methyl molecule?

Answer 25

A molecule that can turn off (silence) genes (CH3)

Question 26

How can an epigenome be changed and passed on?

Answer 26

Diet, behavior, surroundings, environmental pollution, smoking. Epigenetic signals from environment can be passed one generation to the next.

Question 27

When is the critical period for passing on epigenetics?

Answer 27

Gamete formation

Question 28

Which genes involved in cell cycle control and cancer should be targets for methylating drugs in cancer?

Answer 28

Abnormal DNA methylation can silence tumor suppressor genes or activate oncogenes, disrupting normal cell cycle control. Targeting these genes with methylating drugs could potentially reverse or modify the epigenetic alterations.

Question 29

What have twin studies revealed about epigenetics?

Answer 29

Identical twins (monozygotic) have the same DNA sequence, however, epigenetic differences (such as DNA methylation and histone modifications) can cause differences in gene expression, leading to some variations in traits and susceptibility to diseases, even though their genetic code is identical. So, while their genes are the same, their gene expression can differ due to environmental factors.

Question 30

What were the critical periods for grandparents in the Overkalix studies, investigating how grandparents' diets and environmental factors could influence the health and traits of their descendants?

Answer 30

Critical times identified in these studies include: Grandfather's diet during childhood: If a grandfather experienced poor nutrition during childhood, it was linked to an increased risk of diabetes in his grandchildren. Grandmother's diet before conception: When a grandmother experienced food scarcity before conception, it affected the grandchildren's cardiovascular health and lifespan. These findings suggest that early-life nutrition of grandparents, particularly during critical periods such as childhood and pre-conception, can epigenetically influence the health of future generations.