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

What is transcription initiated by?

Answer 9

RNA polymerase holoenzyme

Question 10

First stage of transcription in prokaryotes; INITIATION

Answer 10

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

Question 11

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

Answer 11

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

Question 12

First stage in elongation in transcription of prokaryotes?

Answer 12

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 13

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

Answer 13

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

Question 14

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

Answer 14

Rho Independent Termination

Question 15

What is termination of transcription controlled by?

Answer 15

GC rich-stop sequences in DNA

Question 16

What is a GC-rich sequence?

Answer 16

DNA segment that is rich in guanine & cytosine bases

Question 17

How is termination of transcription controlled?

Answer 17

BY GC-rich stop sequences in DNA

Question 18

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

Answer 18

mRNA transcript forms a stem loop

Question 19

Which pairings help detachment from DNA template?

Answer 19

A-U pairings

Question 20

What is the role of Rho in termination?

Answer 20

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

Question 21

How can transcription in prokaryotes be terminated?

Answer 21

Rho independent/Rho dependent mechanism

Question 22

Why does RNA pol II have a C-terminal domain (CTD) tail?

Answer 22

Recruits eukaryotic mRNA

Question 23

How many RNA polymerases in eukaryotes?

Answer 23

3

Question 24

What are the 3 RNA polymerases in eukaryotes?

Answer 24

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

Question 25

Name given to RNA before they are fully processed?

Answer 25

Heterogenous nuclear RNA (hnRNA) or pre-mRNA

Question 26

Where does eukaryotic transcription take place?

Answer 26

Inside the nucleus

Question 27

Where does prokaryotic transcription take place?

Answer 27

Cytoplasm

Question 28

What is polyadenylation?

Answer 28

Process of adding adenosine nucleotides (A) to the 3' end of mRNA

Question 29

What is capping?

Answer 29

7-methylguanosine cap formed at the 5' end of mRNA

Question 30

What is the primary transcript called prior to processing?

Answer 30

Heterogenous nuclear RNA (hnRNA) or pre-mRNA

Question 31

Define exons

Answer 31

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

Question 33

Define introns

Answer 33

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

Question 34

Define splicing

Answer 34

Complex of proteins that removes introns

Question 35

Define alternative splicing

Answer 35

Exons from the same gene are joined in different combinations

Question 36

Define co-transcriptional

Answer 36

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

Question 37

Function of 5' capping

Answer 37

Essential for mRNA stability