3.8.2.2 Regulation of transcription and translation

Question 1

what are transcription factors

Answer 1

proteins which stimulate or inhibit transcription of specific target genes in eukaryotes by binding to a specific DNA base sequence on a promoter region

Question 2

Describe how transcription can be regulated using transcription factors

Answer 2

1. Transcription factors move from cytoplasm to nucleus
2. Bind to specific promotor regions near the start of their target gene
3. This stimulates or inhibits transcription/ production of mRNA of target gene by helping or preventing RNA polymerase binding

Question 3

Explain how oestrogen affects transcription

Answer 3

1. Oestrogen is a lipid soluble steroid hormone so diffuses into cells across phospholipid bilayer
2. in cytoplasm oestrogen binds to its receptor, an inactive transcription factor, forming an oestrogen - receptor complex
3. This changes the shape of the inactive transcription factor forming an active transcription factor
4. The complex diffuses from cytoplasm into the nucleus
5. Then binds to specific DNA base sequence on the promoter region of a target gene
6. Stimulating transcription of target genes forming mRNA by helping RNA polymerase to bind

Question 4

explain why oestrogen only affects target cells

Answer 4

other cells do not have oestrogen receptors

Question 5

Describe what is meant by epigenetics

Answer 5

Heritable changes in gene function without changes to the base sequence of DNA
Caused by changes in the environment

Question 6

Describe what is meant by epigenome

Answer 6

a chemical modification of DNA and histone proteins
methyl groups on DNA and
Acetyl groups on histones

Question 7

explain how methylation can inhibit transcription

Answer 7

1. Increased methylation of DNA so methyl groups are added to CpG site in DNA
2. Nucleosomes pack more tightly together
   3.Preventing transcription factors and RNA polymerase binding to promoter

Question 8

explain how decreased acetylation of associated histones can increase rate of transcription

Answer 8

1.Dna is wound around histones to form chromatin
2. If acetyl groups bind to chromatin, this reduces attraction of histones to dna
3. Chromatin is relaxed
4. Easier for transptional machinery to bind to DNA which increases rate of transcription

Question 9

explain relevance of epigenetics on disease development and treatment

Answer 9

Environmental factors can lead to epigenetic changes
These can stimulate or inhibit expression of certain genes that can lead to disease development
Increased methylation of DNA/decreased acetylation of histones inhibits transcription
Decreased methylation of DNA/ Increased acetylation of histones stimulates transcription
Diagnostic tests can be developed that detects these epigenetic changes before symptoms present
drugs can be developed to reverse epigenetic changes

Question 10

I Made Dog Doodoo And Heard Its Tasty

Answer 10

Increased
Methylation
of DNA
/Decreased
Acetylation
of Histones
Inhibits
Translation

Question 11

What is RNA interference (RNAi)

Answer 11

in eukaryotes and some prokaryotes, translation of the mRNA produced from target genes can be inhibited by RNAi

Question 12

What do tumour suppressor genes and oncogenes do?

Answer 12

TSGs - slow does mitosis and cause cell death if DNA copying errors are detected
Oncogenes trigger mitosis to occur.

Question 13

Role of epigenetics in cancer

Answer 13

TSGs could become hypermethylated and then inactivated
Oncogenes could become hypomethylated and thenerminantly switched on.