Translation (Lec. 11)

Question 1

What are introns and exons?

Answer 1

Exons are part of a gene that actually code for amino acids (EXons are EXpressed). Introns are noncoding segments interspersed among exons.

Question 2

What direction is mRNA read?

Answer 2

5’ to 3’

Question 3

In what direction are proteins synthesized?

Answer 3

From amino to carboxyl terminus

Question 4

How does mRNA come about?

Answer 4

The code from the DNA template strand is copied with complementary base pairs, which results in a single strand of mRNA (transcription)

Question 5

What is the role of tRNA?

Answer 5

tRNA has special areas that contain a specific anticodon that allows each tRNA to carry only a specific amino acid. This anticodon has complementary base pairs with a codon of mRNA, so at the ribosome it adds its specific amino acid to a growing polypeptide chain

Question 6

What do all tRNAs have in common?

Answer 6

A CCA sequence at the 3’ end where the amino acid will attach

Question 7

What do aminoacyl tRNA synthetases do?

Answer 7

There’s 20 different ones; each catalyzes a specific amino acid-tRNA combination

Question 8

What is the role of rRNA?

Answer 8

It’s a structural component of ribosomes, and it helps to translate the message from mRNA into polypeptide.

Question 9

What happens in the initiation stage of translation?

Answer 9

A small ribosomal subunit binds with mRNA, and moves along the mRNA until it reaches a start codon (AUG). Initiation factors bring in the large subunit that completes the translation initiation complex.

Question 10

What are the three tRNA binding sites?

Answer 10

A site: holds the tRNA with the next amino acid to be added to the chain.
P site: holds the tRNA carrying the growing polypeptide chain.
E site: releases the tRNAs from the ribosome

Question 11

What is the decoding center?

Answer 11

It’s in the small subunit and it recognizes correct pairs and discriminates against mismatches