Lecture 16 - gene expression - transcription

Question 1

What is ‘the flow’ of the Central Dogma of Molecular Biology.

Answer 1

DNA replication; from existing DNA to make new DNA
Transcription; from DNA to make new RNA
Translation; from RNA to make new proteins

Question 2

What are the macromolecules of the Central Dogma of Molecular Biology.

Answer 2

DNA, RNA, protein

Question 3

What are the three stages of transcription?

Answer 3

initiation, elongation, termination

Question 4

What macromolecule is being synthesised during transcription and in which direction is the synthesis proceeding?

Answer 4

RNA 5’ to 3’

Question 5

What is the template for transcription and in which direction does it run?

Answer 5

template strand of DNA 3’ to 5’

Question 6

What happens during initiation of transcription?

Answer 6

1. transcription factors bind to the TATA box and other regions of the promoter
2. RNA pol II binds to form a transcriptional initiation complex
3. two DNA strands separate and RNA pol II starts mRNA synthesis

Question 7

What happens during elongation of transcription?

Answer 7

RNA pol II uses template strand of DNA and inserts complementary RNA nucleotides in the 5’ to 3’ direction

Question 8

Which part(s) of a gene is transcribed from DNA to mRNA?

Answer 8

5’ UTR, coding sequence and 3’UTR (UTR = untranslated region)

Question 9

Which part(s) of a gene is translated from mRNA to protein?

Answer 9

only the coding sequence

Question 10

What is the function of the promoter region?

Answer 10

it is the DNA segment recognised by RNA polymerase so it can initiate transcription

Question 11

Which region of the promoter is particularly important and why?

Answer 11

AT rich region (TATA box), there are only 2 hydrogen bonds so it is easier to pull apart

Question 12

What is/are the main function/s of the UTRs?

Answer 12

5’ UTR facilitats the addition of 5’G cap and the 3’UTR facilitates the addition of the poly-A tail

Question 13

Explain why mutations in non-coding regions may be harmful.

Answer 13

it can disrupt the normal gene expression

Question 14

In eukaryotes, what are the three main functions of the 5’ G cap.

Answer 14

prevents mRNA degradation, promote intron excision and provides binding site for the small ribosomal subunit

Question 15

In eukaryotes, what are the main functions of the Poly-A tail.

Answer 15

prevent mRNA degradation, facilitates export of the mRNA from the nucleus to the cytoplasm

Question 16

Describe the 2 types of coding sequence of DNA.

Answer 16

Exon; part of DNA that will be expressed and become the functional gene product
Introns; intervening sequences in between exons

Question 17

Describe the process of splicing and at which point it occurs.

Answer 17

Introns are removed for the exons to come together in between pre-mRNA to mRNA