Biochemistry of RNA

Question 1

What are the main components of RNA

Answer 1

usually single stranded
forms loops
ribose/uracil

Question 2

What is the function of rRNA

Answer 2

combines with proteins to form ribosomes

Question 3

what is the function of tRNA

Answer 3

carries the amino acids to be added to polypeptide chain

Question 4

what is the function of mRNA

Answer 4

carries the genetic information (copy of DNA strand from template)

Question 5

What structures are found on tRNA

Answer 5

anticodon loop
amino-acid attachment site
3’ OH

Question 6

What enzyme is needed to form RNA

Answer 6

RNA polymerases

Question 7

How many types of RNA polymerase do eukaryotic cells have

Answer 7

3

Question 8

What are the steps of transcription

Answer 8

RNA polymerase binding
DNA chain separation
initiation
elongation
termination

Question 9

What is needed for RNA polymerase to bind

Answer 9

transcription factors

Question 10

What happens during RNA polymerase binding

Answer 10

ribosomal subunit detects promotors needed to initiate transcription

Question 11

Why is the DNA chain separated during transcription

Answer 11

to gain access to the nucleotide sequence

Question 12

What happens when transcription is initiated

Answer 12

First nucleotide to start RNA chain is selected

Question 13

What is the purpose of elongation

Answer 13

to add more nucleotides to the growing chain of RNA

Question 14

What happens during termination

Answer 14

finished RNA chain is released

Question 15

What is the promotor for Polymerase II

Answer 15

TATA box (TBP)

Question 16

How does a transcription factor alter transcription

Answer 16

determines the start and direction
provides a landing platform for polymerase

Question 17

How is transcription completed at low basal rates?

Answer 17

Transcription factor (TFIID) remains at the promotor, new initiation complex can assemble

Question 18

What direction is an RNA chain synthesised in

Answer 18

5’ to 3’

Question 19

what happens after DNA leaves the transcription bubble

Answer 19

it is rewound

Question 20

What direction does RNA move ALONG THE DNA TEMPLATE

Answer 20

3’ to 5’, as the RNA chain is made in a 5’ to 3’ direction

Question 21

How is the finished RNA strand terminated

Answer 21

sequence ends with a series of U’s which are recognised and cleaved by an enzyme

Question 22

What are specific transcription factors

Answer 22

DNA-binding proteins containing 2 domains

Question 23

What are the 2 domains of specific transcription factors

Answer 23

DNA-binding domains
transcriptional activation domain

Question 24

What are enhancers

Answer 24

Sections of DNA activator proteins bind to which enhance the activity of a promotor

Question 25

Do enhancers have to be directly near a promotor

Answer 25

No

Question 26

How is gene expression coordinated

Answer 26

stressors activate transcription of a regulatory protein.
This binds to SRE’s, stimulating transcription of specific genes
code for proteins required for response

Question 27

As introns and exons are transcribed together, how does mRNA not include introns?

Answer 27

Introns are cleaved before translation via splicing

Question 28

What is the difference between pre-mRNA and mature mRNA

Answer 28

addition of 5’ G cap
Poly A tail

Question 29

why is the g cap important

Answer 29

Marks RNA as a messenger
important for stability

Question 30

Why is the poly A tail added

Answer 30

marks end of RNA, stops translation

Question 31

How is transcription and translation compartmentalised in eukaryotes

Answer 31

Begins in nucleus and ends in cytosol (protein synthesised)