L21 RNA Translation

Question 1

What is translation

Answer 1

Translation of nucleotide sequence of mRNA(codons) in to an amino acid sequence of a protein

Question 2

What are requirements of translation

Answer 2

▪️mRNA as carrier of genetic info
▪️tRNA as an adapter molecule which recognizes an amino acid on end and its corresponding codon on the other end
▪️ribosomes for protein synthesis

Question 3

What is the genetic code

Answer 3

Relationship between nucleotide sequence in DNA or mRNA and amino acids in polypeptide chain

Question 4

Whats the start codon

Answer 4

AUG(methonine)

Question 5

What are the stop codons

Answer 5

UAA
UAG
UGA

Question 6

In which direction is genetic info read along mRNA

Answer 6

5’ to 3’ direction

Question 7

What are the characteristics of genetic code

Answer 7

▪️Genetic code is degenerate(multiple codons can code for same amino acid except tryptophan and methionine)
▪️unambiguous(each codon specifies no more than one amino acid)
▪️non overlapping and commaless
▪️universal

Question 8

What are the protein biosynthesis stages

Answer 8

Initiation
Elongation
Termination

Question 9

Describe initiation

Answer 9

▪️80s ribosome dissociated in to 40s and 60s
▪️eIF-3 and 1 bind to 40s subunit preventing re association
▪️GTP and IF-2 bind in addition to binding of mRNA and methionine to tRNA
▪️re association of both subunits

Question 10

What is tRNA charging

Answer 10

Recognition and attachment of specific amino acid to the 3’ hydroxyl adenosine terminus of tRNA in an ester linkage (requires hydrolysis of an ATP to an AMP)

Question 11

Describe elongation

Answer 11

▪️binding of aminoacyl-tRNA to A site
▪️peptide bond formation: tRNA in A site attacks carboxylic group of peptidyl-tRNA in P site (needs peptidyl transferase)
▪️translocation:upon removal of peptide bond from tRNA in P site the discharged tRNA quickly dissociates
▪️eEF-2 and GTP are responsible for translocation of newly formed peptidyl-t-RNA from A site to P site

Question 12

Describe termination

Answer 12

▪️Stop codon appears in A site
▪️Releasing factors recognize stop codon
▪️eRFS,GTP and peptidyl transferase promote hydrolysis of bond between peptide chain and t-RNA at P site

Question 13

What are aims of protein maturation

Answer 13

Activation of protein to a functional form
Localization in subcellular compartment
Secretion from cell

Question 14

What is protein folding

Answer 14

Folding to 3D Stuctures aided by molecular chaperone

Question 15

Whats a proteolysis (in post translational processing)

Answer 15

Means removal of amino terminal,carboxy terminal or internal sequences

Question 16

Describe modifications of individual amino acids

Answer 16

Hydroxylation: of proline and lysine for collagen synthesis
Phosphorylation: of serine theornine or tryosine
Y carboxylation of glutamic acid in prothrombin and osteocalcin

Question 17

Describe addition in certain groups

Answer 17

Glycosylation: attachment of CHO side chain to form glycoproteins
Acylation: addition of fatty acids to various amino acid side chains

Question 18

What antibiotics work by altering translation of bacterial DNA

Answer 18

Tetracyclines

Macrolides like erthromycin

Question 19

What toxins can cause death by inhibiting eukaryotic translation

Answer 19

Shiga toxin(by e coli and causes bloody bacteria) inhibits tRNA binding by acting on 60s subunit
Diptheria toxin (by bacertia and causes diff breathing,heart failure and paralysis) inhibits translocation through binding to eukaryotic EF-2