L5 - DNA Modifications - Adding information to the genetic code

Question 1

What is DNA methylation ?

Answer 1

Addition of a methyl group to cytosine, regulating gene expression without changing DNA sequences

Question 2

What is the main effect of promoter methylation ?

Answer 2

Gene silencing

Question 3

Roles of DNMT enzymes ?

Answer 3

• DNMT1 - maintenance
• DNMT3A/3B - de novo methylation

Question 4

Difference between passive and active demthylation ?

Answer 4

PASSIVE - lost during replication
ACTIVE - enzymatic removal

Question 5

What are CpG islands and their function ?

Answer 5

• CpG-rich promoter regions
• Usually unmethylated - active genes
• Methylation - long-term silencing

Question 6

What is epigenetic inheritance ?

Answer 6

Transmission of gene expression patterns without DNA sequence change

Question 7

What is 5hmC and its role ?

Answer 7

• Oxidised form of 5mC
• Involved in demthylation
• Associated with active genes

Question 8

How does bisulfite sequencing work ?

Answer 8

-Unmethylated C - T
- Methylated C remains C
- Single-base resolution

Question 9

Limitations of bisulfites sequencing ?

Answer 9

Cannot distinguish 5mC from 5hmC

Question 10

What is the barker hypothesis ?

Answer 10

Early life environment influences adult disease risk via epigenetics

Question 11

Example supporting the barker hypothesis ?

Answer 11

Dutch Hunger Winter - long-term health effects

Question 12

Role of SRD5AI in epigenetics ?

Answer 12

• Steroid metabolism gene
• Altered methylation after early life stress
• Links environment to reproductive phenotype

Question 13

Why is DNA methylation important in development ?

Answer 13

Essential for normal development, knockout is lethal

Question 14

Why is DNA methylation considered an epigenetic mechanism ?

Answer 14

It alters gene expression without changing DNA sequences and can be inherited through cell division.