Translation of the Genetic Message

Question 1

Overview of translation

Answer 1

AA are activated and fused to tRNA

Aminoacyl-tRNA combines with ribosomes and mRNA

AA are joined in the ribosome to make a polypeptide in the order specified by the mRNA sequence

the polypeptide chain is terminated

Question 2

What part of the ribosome catalyzes formation of peptide bond between growing polypeptide and incoming AA

Answer 2

large subunit

Question 3

How are 4 bases of DNA and RNA decoded into protein

Answer 3

Adaptor hypothesis

Question 4

Translation requires

Answer 4

mRNA-contains the codons
tRNAs-contains the anticodons
- 3’ end of tRNA carries a specific AA
Ribosome

Question 5

Ribosomal RNA makes up what percentage of RNA

Answer 5

85%

Question 6

Three types of RNA used in protein synthesis

Answer 6

rRNA
tRNA
mRNA

Question 7

An AA gets matched to tRNA by a

Answer 7

tRNA synthetase
forms a covalent bond

Question 8

the aminoacylation has two steps and requires

Answer 8

free energy from ATP

Question 9

Two steps of aminoacyl-tRNA synthetase reactions

Answer 9

activation of AA- reacts with ATP to form aminoacyl-adenylate- irreversible step

conjugation of AA to ribose of 3’ adenylate of tRNA- forms an aminoacyl-tRNA and AMP

Question 10

What is the irreversible step of aminoacyl-tRNA synthetase reaction

Answer 10

activation of AA

Question 11

Amino acid + tRNA + ATP ->

Answer 11

aminoacyl tRNA + AMP + PPi

Question 12

the genetic code is read by tRNA molecules in sets of three consecutive nucleotides in mRNA called a

Answer 12

codon

Question 13

Each codon specifies

Answer 13

one particular AA used in a protein

Question 14

Codon triplet is

Answer 14

non-overlapping
comma-less
degenerate
universal

Question 15

Reading frame is

Answer 15

important
3 bases-codon

Question 16

Start codon

Answer 16

AUG methionine

Question 17

Stop codons

Answer 17

UAA
UAG
UGA

Question 18

Many codons are

Answer 18

degenerate or redundant

Question 19

two or more codons may code for

Answer 19

the same AA

Question 20

How is degeneracy of the code possible with base pairing

Answer 20

certain tRNAs can recognize more than one codon because of adaptable hydrogen bonding

Question 21

wobble

Answer 21

adaptability of tRNAs to recognize more than one codon

Question 22

The wobble base is in which position

Answer 22

5’ position of the anticodon

Question 23

Chain initiation in prokaryotes requires

Answer 23

fmet-tRNA
initiation codon of mRNA
30s ribosomal subunit
50s ribosomal subunit
initiation factors IF-1, IF-2, and IF-3
GTP, Mg 2+

Question 24

Summary of translation initiation in E. coli

Answer 24

1. mRNA and fMEt-tRNA in complex IF-2-GTP bind to the small ribosomal subunit

2.association of large subunit with 30s triggers IF-2 to hydrolyze its bound GTP

3. tRNA bearing the initial fMet is positioned in the P site of the ribosome

Question 25

Chain elongation requires

Answer 25

70s ribosome
mRNA
aminoacyl-tRNAs
elongation factors EF-Tu, EF-Ts, and EF-G
GTP and Mg2+

Question 26

Function of EF-Tu in translation elongation in E. coli

Answer 26

delivers an aminoacyl-tRNA to the A site of the ribosome

anticodon matches the mRNA codon, EF-Tu hydrolyzes its GTP and dissociates from the ribosome, leaving the aminoacyl-tRNA in the A site

tRNA codon and mRNA codon are mismatched the aminoacyl-tRNA dissociates before EF-Tu hydrolyzes GTP

Question 27

E. coli ribosomal elongation cycle

Answer 27

delivery of aminoacyl-tRNA

peptidyltransferase

translocation

EF-G-GDP

Question 28

Translation termination in E. coli

Answer 28

ribosome recycling factor