L8: Protein Synthesis I

Question 1

What does the central dogma states?

Answer 1

Genetic information only flows from DNA to RNA

Question 2

3 key differences between DNA & RNA

Answer 2

1) DNA is double stranded, RNA is single stranded
2) RNA sugar is ribose, and has OH group at 2’ position
3) DNA bases: ACGT
RNA bases: ACGU

Question 3

Function of mRNA

Answer 3

Encodes proteins

Question 4

Function of rRNA

Answer 4

Structural component of the ribosome

Question 5

Function of tRNA

Answer 5

Delivers amino acids to ribosome

Question 6

Which RNA is produced from a DNA template?

Answer 6

mRNA

Question 7

What molecule does the polymerisation of ribonucleoside triphosphate into RNA?

Answer 7

RNA polymerase

Question 8

3 parts of the mechanism of transcription

Answer 8

1) Initiation
2) Elongation
3) Termination

Question 9

First stage of transcription in prokaryotes; INITIATION

Answer 9

Short recognition sequences in the promotor region align RNA polymerase at the transcription start site

Question 10

What happens in transcription in prokaryotes after RNA polymerase is aligned?

Answer 10

Instead of RNA polymerase, a ‘sigma factor’ binds & recruits RNA polymerase

Question 11

Second stage in elongation in transcription of prokaryotes?

Answer 11

1) RNA polymerase unwinds DNA
2) RNA polymerase reads DNA template, synthesising mRNA by adding nucleotides
3) After 1st few nucleotides completed, sigma factor dissociates

Question 12

What happens after the sigma factor dissociates in elongation stage of transcription in prokaryotes?

Answer 12

Addition of nucleotides in the 5’ to 3’ direction, joined by covalent phosphodiester bonds

Question 13

What is another name given to the termination of transcription in prokaryotes?

Answer 13

Rho Independent Termination

Question 14

What is a GC-rich sequence?

Answer 14

DNA segment that is rich in guanine & cytosine bases

Question 15

How is termination of transcription controlled?

Answer 15

BY GC-rich stop sequences in DNA

Question 16

How does mRNA transcript reduce binding of mRNA to DNA template?

Answer 16

mRNA transcript forms a stem loop

Question 17

Which pairings help detachment from DNA template?

Answer 17

A-U pairings

Question 18

What is the role of Rho in termination?

Answer 18

Rho unwinds DNA-RNA duplex, separating growing RNA from DNA

Question 19

How can transcription in prokaryotes be terminated?

Answer 19

Rho independent/Rho dependent mechanism

Question 20

How many RNA polymerases in eukaryotes?

Answer 20

3

Question 21

What are the 3 RNA polymerases in eukaryotes?

Answer 21

1) RNA Pol I
2) RNA Pol II
3) RNA Pol III

Question 22

Why does RNA Pol II have a C-terminal domain ‘tail’?

Answer 22

Recruits processing factors to eukaryotic mRNA & provides binding sites

Question 23

Name given to RNA before they are fully processed?

Answer 23

Heterogenous nuclear RNA (hnRNA) or pre-mRNA

Question 24

Where does eukaryotic transcription take place?

Answer 24

Inside the nucleus

Question 25

Where does prokaryotic transcription take place?

Answer 25

Cytoplasm

Question 26

What is polyadenylation?

Answer 26

Process of adding a tract of adenosine nucleotides to the 3’ of most eukaryotic mRNA molecules

Question 27

What is the primary transcript called prior to processing?

Answer 27

Heterogenous nuclear RNA (hnRNA)
or
pre-mRNA

Question 28

Define exons

Answer 28

Regions of DNA that are coding regions & found in mature mRNA

Question 29

Define introns

Answer 29

Regions of DNA that are non-coding & not found in mature mRNA

Question 30

Define splicing

Answer 30

Complex of proteins that removes introns

Question 31

Define alternative splicing

Answer 31

Exons from the same gene are joined in different combinations

Question 32

Define co-transcriptional

Answer 32

Splicing & capping of eukaryotic mRNA’s happening whilst transcription is ongoing

Question 33

Function of 5’ capping

Answer 33

Essential for mRNA stability