3.8.2.2: Regulation of transcription and translation

Question 1

What is the promoter region?

Answer 1

One or more base sequences found upstream of a gene that control the expression of that gene

Question 2

What are transcription factors?

Answer 2

Proteins which when activated bind to the promoter region of a gene stimulating RNA polymerase to begin transcription of the target gene

Question 3

Activation of transcription: oestrogen (9)

Answer 3

1) Oestrogen diffuses through the phospholipid cell membrane
2) Diffuses through nuclear envelope
3) Binds to oestrogen receptors (complementary)
4) Changes tertiary strict
5) Causes the release of transcription factors
6) Transcription factor binds to DNA (complementary)
7) at promoter region
8) Stimulate RNA polymerase to transcribe gene
9) Increases transcription so mature mRNA is produced

Question 4

What is epigenetics?

Answer 4

Inheritable changes in gene expression without changes to the DNA case sequences

Question 5

Describe methylation of DNA

Answer 5

1) Increased methylation of DNA inhibits transcription

2) Attaches to cytosine base so it prevents transcriptional factors from binding and attracts proteins that condense the DNA histone complex

Question 6

How does acetylation of histones allow gene to be transcribed?

Answer 6

1) Acetylation of histones makes DNA less condensed and unwinds

2) Promoter regions are exposed and transcription factors are able to bind to allows RNA polymerase for transcription

Question 7

What are tumour suppressor genes?

Answer 7

Genes that produce proteins which slow cell division and cause cell death is there’s mistakes in the DNA

Question 8

Describe mutation in the tumour suppressor gene?

Answer 8

The gene becomes inactivated (doesn’t produce the protein) so it stops inhibiting cell division so rate of cell division increases

Question 9

Describe increased methylation of DNA on tumour suppressor genes

Answer 9

• Gene silenced
• Cell cycle activated

Question 10

Describe decreased methylation of DNA on tumour suppressor genes

Answer 10

• Gene activated
• Cell cycle inhibited

Question 11

Describe decreased acetylation of histones on tumour suppressor genes

Answer 11

• More DNA-histone complexes formed
• Promoter regions less accessible
• Cell cycle activated

Question 12

Describe increased acetylation of histones on tumour suppressor genes

Answer 12

• Fewer DNA- histone complexes formed
• Promoter regions more accessible
• Cell cycle inhibited

Question 13

What are proto-oncogenes?

Answer 13

Genes that code for proteins which stimulate and increase the rate of cell division

Question 14

What happens when the proto-onco gene is mutated?

Answer 14

• Becomes an oncogene
• Over stimulation of cell division, gene permanently switched on
• Causing a tumour, a mass of cells

Question 15

Describe increased methylation of DNA on proto-onco genes

Answer 15

• Gene silenced (less transcription factors)
• Cell cycle inhibited

Question 16

Describe decreased methylation of DNA on proto-onco genes

Answer 16

• Gene is activated (more transcription factors)
• Cell cycle accelerated

Question 17

Describe decreased acetylation of histones on proto-onco genes

Answer 17

• More DNA-histone complexes formed
• Less promoter regions accessible
• Cell cycle inhibited

Question 18

Describe increased acetylation of histones on proto-onco genes

Answer 18

• Less DNA-histone complexes formed
• More promoter regions accessible
• Cell cycle activated

Question 19

Describe the control of translation

Answer 19

1) miRNA or siRNA binds to an enzyme in the cytoplasm to create a RNA-induced silencing complex

2) the miRNA/siRNA has complementary base sequence to a specific mRNA molecule

3) This hydrolyses the mRNA by RNA hydrolase

4) Or prevents the ribosome from attaching to the mRNA. mRNA is hydrolysed

Question 20

Why might a specific protein still be produced?

Answer 20

• Not all mRNA has been destroyed so some translation has occurred