NAGE 3

Question 1

What is always the initial product of gene expression?

Answer 1

ALWAYS RNA
it may be functional like snRNA, rRNA or tRNA
or it may be mRNA

Question 2

What is transcription?

Answer 2

the process in which nucleotide info in DNA is copied into RNA

Question 3

What is the difference between the antisense strand and sense strand?

Answer 3

Antisense strand is used to complementary base pair with ribonucleotides whereas the sense strand is not. The sense strand looks identical to the ribonucleotide sequence.

Question 4

Outline the functions of the RNA Polymerases

Answer 4

RNA Polymerase I- transcribes rRNA genes
RNA Polymerase III - transcribes tRNA and 5S RNA genes
RNA Polymerase II - transcribes genes into mRNA

Question 5

What are transcription factors?

Answer 5

DNA binding proteins that regulate the level of transcription from a given gene. Transcriptional activators activate gene expression whilst Transcriptional repressors suppress gene expression. They act collectively to bring about cell specific/inducible/developmental gene expression/

Question 6

First step of transcription

Answer 6

TFIID binds to TATA.
TFIID contains TATA Binding Proteins and TATA Binding Proteins Accessory Factors (TAFs).
This partially unwinds the DNA sequence and widens the minor groove to allow extensive contact with the DNA bases. The unwinding is asymmetrical with respect to the complex to ensure that the transcription is unidirectional.

Question 7

Second step of transcription

Answer 7

TFIIA and TFIIB bind. TFIIB is particularly important because it able to bind to TFIID and RNA Polymerase II

Question 8

Third step of transcription

Answer 8

RNA Polymerase binds to TFIIB with TFIIF bound to the polymerase

Question 9

Fourth step of transcription

Answer 9

TFIIE, TFIIJ, TFIIH bind to RNA Polymerase II. This promotes further unwinding of the DNA helix to allow RNA synthesis. This ultimately forms the Basal Transcriptional Complex

Question 10

What is the point of the Basal Transcriptional Complex?

Answer 10

The Basal Transcriptional Complex allows the RNA Polymerase II to be phosphorylated and initiate transcription.

Question 11

2 mechanisms for how TFs work

Answer 11

Without TFs, basal transcriptional complex produces a basal level of transcription

1) TFs bend the DNA so the TFs are able to interact with each other and the basal transcriptional complex to regulate transcription
2) TFs also help to remodel chromatin - so the histone tails are subject to post-translational modification. They can be acetylated which causes the tails to open. So Hyperacetylation correlates with gene expression and hypoacetylation correlates with gene repression.

Question 12

Factors determining TF expression

Answer 12

Cell lineage
Hormones
Growth Factors
Heat, Touch, Light, Voltage
mechanical stress 
Cell contact

Question 13

Outline the relationship between inflammation and transcription factors

Answer 13

NFkB is a TF normally in the cytoplasm
IkB is an inhibitor of NFkB
Initiators of inflammation breakdown IkB so NFkB can migrate to the nucleus and upregulate the transcription of genes to make cytokines. Aspririn inhibits the breakdown of IkB so NFkB remains in the cytoplasm.

Question 14

Relevance of the Oestrogen receptor

Answer 14

Over half of all breast cancers overexpress the oestrogen receptor
The oestrogen receptor is a TF that regulates oestrogen regulated gene.
breast cancer treatment involves the use of anti-oestrogens.