Brains and Epigenetics

Question 1

What is epigenetics?

Answer 1

the readability, or expression, of genes is modified without changing the DNA itself. Chemical tags are added to or removed from DNA in response to changes in the environment. These tags turn genes on or off, offering a way of adapting to changing conditions without inflicting a more permanent shift in our genomes.

Question 2

What are the 2 types of epigenetics?

Answer 2

Direct
Indirect

Question 3

What is direct epigenetics?

Answer 3

DIRECT epigenetics = all of the epigenetic changes that occur during an individual’s lifespan

Question 4

What is indirect epigenetics?

Answer 4

INDIRECT = epigenetic changes that appear to be transmitted across generations as epimutations, in contrast to classical, less frequent genetic mutations

Question 5

What are the 2 major pathways epigenetics occurs?

Answer 5

DNA methylation
Histone Tail Modification

Question 6

Does epigenetics create change in DNA?

Answer 6

No - by it may lead to inheritable change in behavioural phenotypes

Question 7

What does epigenetics mediate?

Answer 7

some behavioural variation/ phenotypic plasticity

Question 8

Phenotypic plasticity can be controlled by what mechanism?

Answer 8

epigenetics

Question 9

What causes eopigenetics?

Answer 9

inherited DNA ‘tags’
Environmental triggers

Question 10

What are the 2 major pathways for epigenetics?

Answer 10

DNA methylation
Histone tail modification

Question 11

What is added to the DNA strand in DNA methylation

Answer 11

Methly (CH3) group

Question 12

What happens when a methly (CH3) group is added to a DNA strand?

Answer 12

Methyl switches on/ off certain genes - allowing/ inhibited gene transcription

Question 13

Give an example of Direct Epigenetics

Answer 13

RATS

• Glucocorticoid receptor (GR) in rat hippocampi binds to secreted cortisol (when stressed)
  When binding occurs, hippocampus signals to hypothalamus to shut down Hypothalamus-Pituitary-Axis (HPA) (mechanism of secreting cortisol)

EPIGENETICS:
- rats that have little care as pups = anxious and neophobic, have greater methylation of GR = less GR ability to stop cortisol production
- rats that have adequate parental care are bolder and more neophilic

The Epigenetics happening here are environmental factors affect the phenotypes being “switched on/ off”

Question 14

Give an example of indirect epigenetics

Answer 14

Franklin et al (2010) subjected neonatal rats to chronic and unpredictable maternal seperation
- as adults = depression syndromes and modified epigenetic patterns in sperm
- similar behavioural and epigenetic patterns found in offspring
[Generational/ inherited trauma]

Question 15

What is histone tail modification?

Answer 15

A major epigenetic mechanism
- acetyl groups are added to histone tails - neutralises positive charge between histone and DNA strand
- makes nucleosome’s grip on DNA looser
process allows transcription of DNA and genes become “active”

Question 16

Give an example of Direct Epigenetics in histone tail modification

Answer 16

Fruit fly (Drosophilia melanogaster)
- life spane increases up to 32% compared to wild-type controls
Heat tolerance decreased by up 55% compared to controls

Question 17

What is somatic epigenetic inheritence?

Answer 17

non-germline epigenetics

Question 18

give an example of somatic epigenetic inheritence

Answer 18

pups in womb
2M females have higher levels of testosterone, high aggression and behaviourally sensitive to testosterone treatments in adulthood than 0M females

Question 19

What are the consequences of 2M females?

Answer 19

• higher testosterone
• more aggressive
• behaviourally sensitive to testosterone treatments
• more likely to produce more male pups

Question 20

How does epigenetics affect evolution/ selection?

Answer 20

• if it aids fitness, may be retained for generations
• if it does not aid fitness, may be lost rapidly
• epigenetics respond to environmental change but may have some degree of inheritence

Question 21

What does epigenetics regulate?

Answer 21

Phenotypic plasticity and evolutionary adaptation (Hu and Barrett, 2017)