Ch.13: Translation of mRNA

Question 1

What are Codons? What is the start codon? What are the stop codons?

Answer 1

genetic information coded within mRNA in groups of 3 nucleotides; Start- AUG; Stop: UAA, UAG, UGA

Question 2

What is a peptide bond?

Answer 2

the linkage between the amino group of the incoming amino acid and the carboxyl group of the existing polypeptide

Question 3

What are 2 characteristics of amnio acids?

Answer 3

Polar: hydrophilic or water loving
(on outside because it can tolerate aqueous environments)

Nonpolar and aromatic:
hydrophobic or water hating
(on inside)

Question 4

What are the 4 levels of structure in proteins?

Answer 4

1. Primary (amino acid sequence)
2. Secondary (formation of a helices and b sheets)
3. Tertiary (final three-dimensional structure)
4. Quaternary (proteins made up of two or more polypeptides)
   -Not all proteins have a quaternary structure (monomeric proteins)

Question 5

What do tRNAs do during translation?

Answer 5

incorporate the incoming amino acid into proteins by the ribosome

Question 6

Describe the structure of tRNA

Answer 6

Has a 3’ ACC acceptor stem where the amino acid is added and the actual tRNA is a ribbon shape twisted molecule

Question 7

What do aminoacyl-tRNA synthetase do?

Answer 7

this enzyme aids in the charging of tRNA by attaching amino acids to the tRNA
- there are 20 of them, 1 for each amino acid

Question 8

Describe tRNAs and the wobble rule

Answer 8

The genetic code is degenerate at the third position of codons because it is the 3rd base of the codon and the 1st base of the anticodon so it can tolerate mismatches

Question 9

What is a ribosome composed of?

Answer 9

two distinct subunits, the large and small subunits (latches to mRNA) that are formed by the assembly of proteins and rRNA

Question 10

What are the 3 discrete sites of ribosomes?

Answer 10

A site: where the next aminoacyl tRNA with an incoming amino acid (1st one) loads into the ribosome
P site: where the peptidyl transfer takes place and the peptide bond is formed (2nd amino acid enters)
E site: where the empty tRNA exits the ribosome after the peptide bond has been formed

Question 11

What is transcriptional/translational
coupling?

Answer 11

As soon an mRNA strand is long enough, a ribosome will attach
to its 5’, end so translation begins before transcription end

Question 12

What antibiotics inhibit the process of translation in bacteria?

Answer 12

chloramphenicol, erythromycin, puromycin, tetracycline and
streptomycin

Question 13

What requires auxiliary proteins?

Answer 13

initiation, elongation, and termination stages of translation in both bacteria and eukaryotes