Wk5 Environmental Effects And Epigenetics

Question 1

What are epigenetic mechanisms?

Answer 1

Environment (infectious agents, toxins, diet etc.)

Question 2

What is phenotype?

Answer 2

Who we are

Genotype + environment

Question 3

Monozygotic twins

Answer 3

Can look different - so environment must have been a factor

Question 4

How do cell types with same genome end up different?

Answer 4

Genes are turned on or off in a specific pattern

Question 5

What regulates gene expression?

Answer 5

Transcriptional control
RNA processing control
RNA transport and localisation control
Translation control
MRNA degradation control
Protein activity control

Question 6

What are genes?

Answer 6

Transcriptional units composed of

• structural information coding for a protein
• regulatory sequences giving instructions for expression

Question 7

What is a gene promoter?

Answer 7

Determines whether transcription starts

Question 8

What are general transcription factors?

Answer 8

Recognise and bind the gene promoter
Recruit RNA polymerase II
Allow a basal level of transcription

Question 9

What are rates of transcription controlled by?

Answer 9

• Enhancers (DNA sequences up & downstream of gene)

- Gene-specific transcription factors (activate and repress)

Question 10

When do chromosomes become visible?

Answer 10

When cell divides at mitosis

Question 11

What are alleles?

Answer 11

Different versions of the same gene

Question 12

What is the histone code?

Answer 12

• a layer of information overlaying the DNA

- involved in turning genes on or off

Question 13

What do enzyme families do?

Answer 13

Modify histone tails

E.g. histone acetylation

Question 14

Can the environment influence histone acetylation?

Answer 14

Yes

Question 15

What are nucleosome modifications?

Answer 15

1. Involved in turning genes on or off
2. Respond to changes in environment inside and outside of the cell
3. (Epigenetic regulation) - can be altered by epigenetic therapies

Question 16

What is dosage compensation in mammals?

Answer 16

• X-inactivation is random
• Occurs in the inner cell mass of the blastocyst.
• Inactive state is passed on to succeeding cell generations (inherited)
• X-inactivation is an example of a heritable epigenetic state

Question 17

What is gene regulation and epigenetic mechanisms?

Answer 17

-DNA is an inert carrier of information.
- Its interpretation (gene expression) defines phenotype
- Environmental effects can impact on gene activity:
- gene specific transcription factors
- epigenetic mechanisms
(i.e. histone modifying enzymes)
- X inactivation (random)
Long term chromosome silencing)