RNA Synthesis

Question 1

What is produced during transcription?

Answer 1

DNA -> mRNA

nucleic acid -> nucleic acid

Question 2

Where does transcription occur?

Answer 2

Nucleus

Question 3

What is produced during translation?

Answer 3

mRNA -> Protein

nucleic acid -> protein

Question 4

Where does translation occur?

Answer 4

In the cytoplasm

Question 5

What are genes made of?

Answer 5

DNA

Question 6

What is the function of DNA?

Answer 6

Stores genetic information of the genotype

Question 7

What is the central dogma theory?

Answer 7

DNA -> RNA -> Proteins

Question 8

Describe what the human genome is

Answer 8

22 autosomes in human genome and a pair of sex chromosomes

Question 9

What are chromosomes?

Answer 9

Vehicles to carry genes

Question 10

What are centromeres?

Answer 10

(primary constriction)

microtubules of spindles joined at centromere to keep sister chromatids attached

Question 11

What is a telomere?

Answer 11

Compound structure at the end of a chromosome (has double stranded ends of 6 base pair repeats

Question 12

How do telomeres protect chromosome ends?

Answer 12

Double stranded ends prevent repair processes in cells joining up the ends to other chromosomes

Question 13

What is the role of pseudogenes?

Answer 13

Duplicates of non functional genes

Question 14

Where are DNA coding regions present on chromosomes?

Answer 14

Coding regions are spread along the chromosome with non coding regions between them

Question 15

What is a gene?

Answer 15

A hereditary protein unit containing the phenotype and regulation regions

Question 16

What are UTRs?

Answer 16

Untranslated regions - non coding mature mRNA

Question 17

What are introns?

Answer 17

non coding RNA

Question 18

What are exons?

Answer 18

Coding RNA

Question 19

What is the promoter?

Answer 19

The region that initiates transcription

Question 20

Where is the promoter found?

Answer 20

Upstream of the transcription start site on the 5’ end

Question 21

How is transcription initiated?

Answer 21

RNA polymerase II binds to the start site on the 5’ end

Question 22

Explain in detail how transcription process occurs?

Answer 22

1. TATA box (basal promoter) recognised by TATA binding protein
   (TBP) in TFIID
2. TFIIA and TFIIB bind
   
   • TFIIA stabilises the compound
3. Other general TF bind
4. RNA Polymerase II assembles at the promoter region forming
   transcription initiation complex
5. TFIIH (helicase) pulls apart DNA and phosphorylates RNA
   polymerase II
   6 Phosphorylated RNA Polymerase II is released from complex
   and transcription begins

Question 23

What are the different Human RNA Polymerases?

Answer 23

RNA Polymerase I - Most ribosomal RNA (rRNA)
RNA Polymerase II - Protein coding, micro RNA (miRNA)
RNA Polymerase III - Transfer RNA (tRNA) and 5S rRNA

Question 24

How do polymerases synthesise RNA?

Answer 24

By using nucleotide triphosphates e.g.

- ATP, CTP, GTP, UTP

Question 25

What is the role of the Kozak sequence?

Answer 25

Enables the ribosome to know that AUG is the start codon to allow translation to begin

Question 26

How is RNA modified?

Answer 26

- 5' Cap - PolyA tail - Splicing

Question 27

What is 5' capping?

Answer 27

7-methylguanosine added to triphosphate bridge on 5' end using the enzyme methyltransferase

Question 28

Explain the role of the 5' cap?

Answer 28

Allows the cell to recognise the mRNA is ready to be exported out of the nucleus

Question 29

How does polyadenylation occur?

Answer 29

1. Specific endonucleases recognise the termination stop codon 2. RNA cleaved off RNA Polymerase II using CPSF 3. Polyadenylate polymerase adds 250 A's to 3' end

Question 30

What is the role of the polyA tail?

Answer 30

Prevents endonucleases digesting the ends of mRNA | Aids transport within the cytoplasm

Question 31

Is there any significance to the length of the polyA tail?

Answer 31

Yes, the longer the polyA tail the more stable the mRNA molecule

Question 32

What are the consequences of mRNA strands not having a 5' cap or 3' polyA tail?

Answer 32

The cap and the tail signal to the cell mRNA is ready to be exported - if either are missing the mRNA remains in the cytoplasm and RNAses will digest it

Question 33

What is splicing?

Answer 33

The removal of introns and joining of exons

Question 34

How does splicing occur?

Answer 34

1. Cleavage at 5' splice site 2. Intron moves allowing GU sequence to link at Branch A 3. Lariat forms 4. AG at 3' end cleaved 5. Causes ligation of exons 6. Introns degraded

Question 35

How is this process regulated?

Answer 35

Enzymatically controlled by spliceosomes snRNPs

Question 36

What are SnRNPs?

Answer 36

Small nuclear ribonucleic proteins

Question 37

How do SnRNPs work?

Answer 37

Bind to both sides of mRNA strand and push out the introns

Question 38

How are multiple proteins with varying functions produced from the same mRNA strand?

Answer 38

Alternative splicing results in differing proteins forming. | Different exons are chosen

Question 39

What further regulations are in place before exporting from the nucleus?

Answer 39

CBC - cap binding complex binds to the capped molecules EJC - exon junction complex binds to a successfully spliced junction

Question 40

How is export from the nucleus regulated?

Answer 40

Modifications are recognised allowing mRNA molecule to be released

Question 41

Where does the mRNA leave the nucleus from?

Answer 41

Through the nuclear pore complex