Molecular basis of gene transciption

Question 1

What are the three stages of transcription?

Answer 1

Initiation
Elongation
Termination

Question 2

Describe initiation stage of transcription

Answer 2

Sigma factor attaches, allows RNA polymerase to associate.
RNA polymerases is directed to start site of transcription on double stranded DNA, enzyme finds transcriptional start site.

Question 3

What is the structure of RNA polymerase

Answer 3

aaBB

Question 4

Describe elongation stage of transcription

Answer 4

Reading of DNA sequence on template and synthesis of messenger RNA

Question 5

Describe termination stage of transcription

Answer 5

Termination site reached, mRNA synthesis finishes

Controlled by STOP sequences in DNA; GC rich regions which means that the RNA transcript form a hairpin loop.

Question 6

What is polyadenylation

Answer 6

Adds AAAAAAAAA….. to the end of the chain

Question 7

Gene regulation by methylation

Answer 7

Methylation can either occur on the histone or on the amino acid; it switches off the gene as it condenses the chromatin

Question 8

Gene regulation by acetylation

Answer 8

Acetylation occurs on the histone; de-condenses chromatin and so switches on the gene

Question 9

Rett syndrome

Answer 9

Mutation in methyl CpG binding protein 2 (MECP2)

Highly expressed in neurones, binds to methylated CpG regions; forms complex and silences gene expression.
Lower levels of protein lead to disturbed neuronal function.