Epigenetics

Question 1

What is the difference between a phenotype and a genotype?

Answer 1

Phenotype is how it displays (environment interaction) and genotype is the genetic information - carried in chromosomes

Question 2

What is an allele?

Answer 2

The variants of a gene

Question 3

What does epigenetics mean?

Answer 3

The way you can change how the DNA is expressed based on things binding to it / changing the DNA sequence - inherited change in phenotype

Question 4

What environmental factors can effect epigenetics?

Answer 4

Developmental (childhood)
Environmental chemicals
Drugs
Ageing
Diet

Question 5

What are the types of epigenetics?

Answer 5

DNA methylation - methyl group (a factor found in some diets) can tag DNA and activate or repress genes

Histone modification - the binding of epigenetics to histone tails alters the extension to which DNA is wrapped around histones and availability of genes in the DNA to be activated

Question 6

What are histones?

Answer 6

Proteins around which DNA can wind for compaction and gene regulation

Question 7

Epigenetics and the environment

Answer 7

Some stable throughout life and some affected from the environment

Question 8

What does maternal care lead too?

Answer 8

Maternal care (pup licking) switches on serotonin, acts through 5-HT7 receptor to activate transcription factor NGFIA which switches on gene which expresses glucocorticoid receptor - this controls the response to stress and keeps anxiety levels stable

Question 9

What does absence of maternal care lead too?

Answer 9

Can’t switch on the receptor, there is no transcription factor there to do it, so the gene becomes metholated (switched off). Without GR, loss of feedback in HPA axis, increased stress hormones , so increased anxiety and depression

Question 10

What does transgenerational epigenetics mean?

Answer 10

Environmental influence on parents can affect off spring

- distrusted histones in sperm cells, show altered RNA profile in offspring and grand offspring

Question 11

What is genomic imprinting?

Answer 11

A form of epigenetics that causes genes to be expressed in a parent-of-origin-specific manner - some genes are switched off depending if they are inherited maternally or paternally - it is reversible in the next generation

Question 12

What does a gene mean if it is imprinted?

Answer 12

It is there but the disease does not display

if it is inherited by the father, the paternal copy is switched off so if inherited, the gene is carried but not active

these children will pass the faulty gene to their offspiring
if it has been imprinted from their father, the female offspring have a 50% chance of carrying it and fi they do, it will be active and the disease will display. The male offspring have a 50% chance of carrying it, but it will be imprinted, so they will be carriers

Question 13

How many copies of the gene do you need to have a condition in genomic imprinting?

Answer 13

One copy is sufficient enough but it needs to be active

Question 14

What does chromosomal deletion mean?

Answer 14

During meiosis, a spontaneous deletion of part of a chromosome may occur

Question 15

What chromsome is susceptible to deletion?

Answer 15

15

Question 16

What does maternal imprinting mean?

Answer 16

the paternal genes are active

Question 17

What does paternal imprinting mean?

Answer 17

the maternal genes are active

Question 18

What do syndromes in genomic imprinting have the same?

Answer 18

Genotype - but it depends when the deletion happens. Same genotype but different phenotype

Question 19

If deletion on paternal chromosome - paternal imprinted, what disease is caused?

Answer 19

Prader-Willi - genetic deletion on chromosome 15 of segment 11-13

Question 20

If deletion on maternal chromosome - maternal imprinted - what disease is caused?

Answer 20

Angelman - genetic deletion on chromosome 15 of segment 11-13

Question 21

What is prader willi syndrome?

Answer 21

Charcteristed by intellectual disability, decreased muscle tone, short stature, an a huge appetite - obesity

Question 22

What is angelman syndrome?

Answer 22

Delayed development, severe language impairment, movement and balance problems, epilepsy, small head, sociable behaviour

Question 23

What happens to grandchildren in imprinting?

Answer 23

The children are carriers
If maternally imprinted, the daughter is a carrier, and she won’t pass it on to her children because imprinted - they are all carriers. However, the 50% of the sons children will get it as it hasn’t been switched off

children from dad will get it, but not from the mum