Gene Expression

Question 1

What is the 3 stage process involved in making RNA and making a polypeptide?

Answer 1

Initiation
Elongation
Termination

Question 2

What happens in initiation in transcription?

Answer 2

Promoter recognition
Transcription initiation factors
RNA polymerase

Question 3

What happens in elongation in transcription?

Answer 3

5’ to 3’ chain growth

Question 4

What happens in termination in transcription?

Answer 4

Sequence dependent

Question 5

What does the transcription factor recognise on the DNA sequence?

Answer 5

TATA box

Question 6

What happens after the TATA box has been recognised?

Answer 6

RNA polymerase (promoter) binds over transcription factor 
First building block is produced from the first bases to the left of RNA polymerase - this is where transcription starts

Question 7

What is the mRNA transcript made using?

Answer 7

Makes complementary strand to DNA template strand

DNA coding strand not used in transcription

Question 8

Which direction does transcription work in?

Answer 8

5’ to 3’

Question 9

What is RNA processing and what does it include?

Answer 9

When pre-mRNA is made into mature mRNA

Capping, tailing/polyadenylation, splicing

Question 10

What is capping?

Answer 10

Methylated guanine added to 5’ end of sequence in a 5’-5’ linkage
Provides protection and plays role in translation

Question 11

What is polyadenylation?

Answer 11

Adding a polyA tail to 3’ end of sequence
Uses specific endonuclease to cleave site from RNA polymerase
Uses polyA polymerase to add polyA tail

Question 12

What is splicing?

Answer 12

Introns are removed from pre-mRNA to leave coding sections which are joined together
Produces mature mRNA

Question 13

What is the structure of ribosomes in prokaryotes?

Answer 13

3 rRNAs and 56 proteins
30S and 50S subunits
70S ribosome

Question 14

What is the structure of ribosomes in eukaryotes?

Answer 14

4 rRNAs and 82 proteins
40S and 60S subunits
80S ribosome

Question 15

Describe the features of the genetic code

Answer 15

Triplet code, degenerate
Non-overlapping
‘Comma-less’ (no gaps)
5’ to 3’ templat read through producing N to C polypeptide chain extension
Adaptor molecule needed, tRNA

Question 16

What is the initiation triplet?

Answer 16

AUG

Question 17

What are the termination triplets?

Answer 17

UAA
UAG
UGA

Question 18

tRNA structure formation

Answer 18

When two part of a RNA sequence are complementary, hydrogen bonds can form between the anti-parallel complementary sequences forming a loop

Question 19

Where does the amino acid bind to on tRNA?

Answer 19

Binds to adenine at 3’ end of sequence

Question 20

What is the anticodon?

Answer 20

Section of tRNA (triplet) that is complementary to an mRNA codon

Question 21

What is inosine?

Answer 21

Part of anticodon that can bind to any base
5’ base of anticodon and hence 3’ base of codon is wobble position allowing a single tRNA species to recognise more than one codon

Question 22

What happens in the initiation step of translation?

Answer 22

AUG codon recognition by methionyl tRNA

Occurs at ribosome

Question 23

What happens in elongation of translation?

Answer 23

N to C chain growth

Aminoacyl tRNAs formed

Question 24

What happens in the termination of translation?

Answer 24

Stop codons are reached

Translation stops