Control of transcription

Question 1

Transcription Factors

Answer 1

Proteins that bind to specific DNA sites called promoter regions
They can activate or inhibit transcription

Question 2

Oestrogens role

Answer 2

Oestrogen is a steroid hormone that can initiate transcription
1) Diffuse through the cell membrane because its lipid based
2) Bind to the receptor on the transcription-factor
3) DNA binding site changes shape
4) TF moves into nucleus
5) Complimentary to the DNA so it can move in and initiate transcription

Question 3

Epigenetics

Answer 3

Heritable changes in gene function without changing the DNA base sequence
Caused by changes in the environment
Methylation and Acetylation

Question 4

Methylation of DNA

Answer 4

Increases methylation inhibits transcription
Methyl groups attach to cytosine:
1) Prevents TF from binding
2) Attract proteins that condense the DNA histone complex

Question 5

Acetylation Of DNA

Answer 5

Increased Acetylation stimulates transcription
1) Acetyl groups are negatively charged
2) Acetyl groups bind to the histones decreasing association with DNA ( they bind to acetyl groups instead)
3) Decondenses DNA so it can be transcribed

Question 6

Euchromatin ( Active )

Answer 6

Decreased Methylation
Increased Acetylation of histones

Question 7

Heterochromatin ( silent )

Answer 7

Increased methylation
Decreased Acetylation

Question 8

RNAi RNA interference

Answer 8

-Translation of mRNA produced from target genes is inhibited by RNAi
- an mRNA molecule that’s been transcribed gets destroyed before it’s translated
- done by small interfering RNA siRNA

Question 9

How does RNAi occur

Answer 9

• An enzyme can cut double stranded mRNA into single stranded siRNA
• One strand of the siRNA combines with another enzyme
• siRNA- enzyme complex will bind via complimentary base pairing to another mRNA molecule
• The enzyme can cut up the mRNA into small pieces so it cannot be used in translation