GENE EXPRESSION RECAP

Question 1

Function of rRNA

Answer 1

form core of ribosome and catalyse protein synthesis

Question 2

central dogma

Answer 2

DNA –> RNA –> Protein

Question 3

RNA produced is complementary to __(a)__ and identical to __(b)__

Answer 3

a) template

b) coding

Question 4

Where does PROKARYOTIC TRANSCRIPTION initiate?

Answer 4

• begins at gene promoter which is a region of DNA upstream of a gene

Question 5

What are the roles of sigma factors in initiating transcription? How is this different in eukaryotes?

Answer 5

serve to bind elements of DNA promoters to create DNA polymerase complex

• transcription factors used in eukaryotes to recruit DNA polymerase

Question 6

How is transcription terminated?

Answer 6

intrinsic termination after inverted repeats to form an RNA stem loop

Question 7

RNA polymerase does not require DNA _____

Answer 7

helicase

Question 8

Function of amino-acyl tRNA synthetase

Answer 8

ensures that the the tRNA molecules are charged with the correct amino acids

Question 9

3 translation steps

Answer 9

Initation

Elongation

Termination

Question 10

In prokaryotes, 30S ribosomal complex is recruited to the ___ binding ____.

Answer 10

a) ribosome

b) site

Question 11

Function of initiation factors in translation

Answer 11

helps formyl-Met/initiator tRNA bind to the start codon allowing 50S unit to approach

Question 12

Difference between eukaryotic and prokaryotic ribosomes

Answer 12

eukaryotes have their subunits precharged with Met-tRNA

Question 13

Describe translation

Answer 13

1) initiation codon, usually AUG, positions the reading frame of mRNA
2) translation proceeds from initiation to first stop codon (open reading frame)

3) codons bound to aminoacy tRNA
- each codon linked together by peptide bond at ribosome acceptor A and by a peptidyl transferase

4) peptide chain formed

Question 14

What is an open reading frame?

Answer 14

First start codon to first stop codon

Question 15

How is translation terminated?

Answer 15

release factors which recognise STOP codon release the peptide and ribosome recycling factor causes disassociation of ribosome

Question 16

Majority of eukaryotic genome is ___

Answer 16

introns, non-coding

Question 17

What is a transcription unit in eukaryotes?

The equivalent in prokaryotes?

Answer 17

• has promoter upstream of the 5’ end to recruit RNA pol

- operon

Question 18

Function of transcription factors

Answer 18

to recruit RNA pol

Question 19

What are enhancer sequences?

Answer 19

places that TF’s bind to influence and therefore increase the rate of transcription initiation

Question 20

TATA box is an example of a

Answer 20

promoter region

Question 21

Functional RNA genes are not ______.

Instead?

Answer 21

translated

• they are synthesisesd in the nucleus

Question 22

rRNA is synthesised using RNA pol (a) in the __(b)__

Answer 22

a) 1 b) nucleolus

Question 23

tRNA is synthesised using RNA pol _(a)__ in the __(b)___

Answer 23

a) III b) nucleus

Question 24

mRNA is synthesised using RNA pol __(a)___ in the __(b)__

Answer 24

a) II b) nucleus

Question 25

What is the use for the 5’ cap?

Answer 25

ribosome binding

Question 26

Coding exons must be (a) together before translation. . This occurs in a large complex called the __(b)___ and introns form a __(c)___ structure during removal. ___(d)____ splicing means that one gene can make a variety of __(e)___ products.

Answer 26

a) spliced
b) splicosome
c) lariat
d) alternative
e) protein

Question 27

a) What is a poly-adenylated tail?
b) What is its function?
c) How is it formed?

Answer 27

a) sequence of repeated A bases
b) to protect against degradation and to influence translation
c) AATAAA poly A signal causes the primary transcript to have around 20 bases cleaved downstream of the poly A signal and poly A tail synthesised from that point

Question 28

a) What is muscular dystrophy?

b) distinguish between Duchenne and Becker MD?

Answer 28

a) defects in dystrophin gene Xp21 exons
b) DUCHENNE - no functional protein produced due to deleted exon

BECKER - reading frame maintained giving a semi functioning protein