7.2 Transcription

Question 1

What is transcription?

Answer 1

The transcription of DNA to RNA

Question 2

How can the gene coding for a protein be reckognised?

Answer 2

It begins with a promotor and ends with a terminator

Question 3

What are the steps of transcription?

Answer 3

1. RNA polymerase binds to promotor and unwinds DNA strands (=Initiation)
2. The RNA nucleotides bind to the antisense strand, forming the RNA version of the sense DNA strand (=Elongation)

Question 4

What still needs to be removed from the mRNA? What does that?

Answer 4

Introns need to be removed, Exons are kept. During splicing, a spliceosome removes introns and joins exons.

Question 5

What else is added to the mRNA for protection?

Answer 5

5’ cap
3’ poly-A tail

Question 6

What is alternative splicing?

Answer 6

Selective removal of specific exons, leads to a wider range of proteins that can be produced

Question 7

What do transcription factors do?

Answer 7

They form a complex with RNA polymerase at the promotor, without them the RNA polymerase can’t trnascribe

Question 8

What are the 2 regulatory proteins?

Answer 8

Activator proteins bind to enhancer site, and increase rate of transcription by mediating complex formation
Repressor proteins bind to silencer site and decrease the rate of transcription by ihibiting complex formation

Question 9

How can the environment of an organsim change it’s gene expression?

Answer 9

due to different chemical signals coming from the environment into the cell, the production of certain proteins/the expression of certain genes can be changed

Question 10

How do nucleosomes/protein+histone influence transcription?

Answer 10

Histone proteins have tails that are + charged. DNA is - charged. By adding an acetyl group, the tails are neutralised & let go of the DNA, by adding a methyl group, the tails remain positive. So methylation decreases gene expression.