RNA makes protiens

Question 1

What are ORFs and what are beside them on mRNA?

Answer 1

ORF: translated into protein

Beside the ORF: 5’UTR and 3’UTR

Question 2

What are the start and stop codons?

Answer 2

Start: AUG (codes for Met, M)

Stop: UAA, UAG, UGA (codes for no aa)

Question 3

What is a Shine-Dalgarno sequence?

Answer 3

the sequence in prokaryotic mRNA that comes before the start codon.

Polycistronic mRNA have multiple Shine-Dalgarno sequences as it codes fro multiple proteins.

Question 4

what is a third base in a codon called if it is redundant?

Answer 4

A wobble base

Question 5

DNA that codes for one protein is called…

Answer 5

monocistronic

Question 6

What are four types of mutation?

Answer 6

• Silent
  (wobble base change - does nothing)
• Missense
  (causes a substitution of an aa)
• nonsense
  (introduces a stop codon)
• Frame-shift
  (caused by insertion/deletion of a few nt)

Question 7

Why does tRNA fold to form an L shape?

Answer 7

The D-Loop and TΨCG loop interact

Question 8

What other nucleotides wabble bases enable tRNA to recognise different codons?
(how are they derived)

Answer 8

Inosine (I)
(derived from adenine)

Pseudouridine (Ψ), Dihydrouridine (D), and Thymidine (T)
(derived from Uricil)

Methyl-guanine (mG)
(derived from Guanine)

Question 9

How is tRNa made from precursors?

Answer 9

• pre-tRNA contain many tRNA
• the 5’ end is spliced by RNAse P (a rybozyme)
• the 3’ end is spliced by RNAse D (a protein)
• CCA is added to 3’ end by tRNA nucleotidyl transferase
• base modifications take place (guided by snoRNAs)
• further splicing can take place if needed
• tRNA is charged

Question 10

How is tRNA charged?

Answer 10

a different Aminoacyl-tRNA synthetase for each aa

• an aa is adenylated.
• activated aa then trasfered to 3’OH of tRNA (AMP released)

Question 11

What are the different sites on the ribosome where tRNA attaches to mRNA?

Answer 11

A-site

P-site

E-site