chapter 39

Question 1

In protein synthesis or translation, the mRNA is decoded in what direction

Answer 1

5’ to 3’ one codon at a time

Question 2

protein synthesis is in which direction

Answer 2

amino to carboxyl

Question 3

what are the substrates for protein synthesis

Answer 3

aminoacyl-tRNAs

Question 4

aminoacyl-tRNAs are synthesized by

Answer 4

aminoacyl-tRNA synthetases

Question 5

the synthesis of long proteins requires

Answer 5

a low error frequency

Question 6

what portion of the tRNA molecule base pairs with the mRNA codon

Answer 6

anticodon

Question 7

what are the 8 general characteristics of tRNA molecules

Answer 7

1. Each is a single strand of RNA
   between 73 and 93
   ribonucleotides in length
   (~25kDa).
2. In a two-dimensional
   representation, all tRNA
   molecules appear as a
   cloverleaf pattern. The
   amino acid accepting region is
   the acceptor stem, which
   contains the 3’ CCA terminal
   region.
3. Stems include base-paired
   nucleotides and loops are not.
4. The 5′ end is
   phosphorylated, and
   the 5′ terminal residue
   is usually pG.
5. The amino acid is
   attached to a hydroxyl
   group of adenosine in
   the CCA region of the
   acceptor stem.
6. The anticodon is in
   a loop near the center
   of the sequence.
7. Transfer RNA molecules contain unusual bases, such as
   inosine, or bases that have been modified.
8. The three-dimensional structure of the molecule is L-shaped.

Question 8

the anticodon that pairs with AUG is

Answer 8

CAU

Question 9

Some tRNA molecules can recognize more than one codon.
The recognition of the third base in the codon by the
anticodon is sometimes less discriminating, a phenomenon
called

Answer 9

wobble

Question 10

what are the two generalizations of the codon-anticodon interaction

Answer 10

1. Codons that differ in either of the first two nucleotides must
   be recognized by different tRNAs.
2. The first base of the anticodon determines the degree of
   wobble. If the first base is inosine, the anticodon can
   recognize three codons.

Question 11

how do aminoacyl tRNA synthetases catalyze the activation of amino acids

Answer 11

1. formation of aminocayl adenylate or aminoacyl-AMP
2. aminoacyl group then transferred to a specific tRNA recognized by the synthetase

Question 12

what are the true translators of the genetic code

Answer 12

Synthetases are the true translators of the genetic code in that they assign
a particular amino acid to a specific tRNA