Lecture 19- Translation

Question 1

What are the two broad categories of mutations that can happen during DNA replication?

Answer 1

Point mutations and frameshift mutations.

Question 2

What types of mutations can point mutations lead to?

Answer 2

Silent mutation: no change in amino acid.
Missense mutation: amino acid is changed for a different one.
Nonsense mutation: amino acid changed to a stop codon. Protein is cut short.

Question 3

What types of mutations can frameshift mutations lead to?

Answer 3

Frameshift mutations can lead to either excessive missense mutations (almost all amino acids changed) or a nonsense mutation.

Question 4

What is the tRNA’s role?

Answer 4

The tRNA will bind to a specific amino acid (at the amino acid attachment site) and will then bind to the codon (using its anticodon region) to deposit the amino acid at the end of a polypeptide.

Question 5

How is the amino acid attached to the tRNA?

Answer 5

Using an aminoacyl-tRNA synthetase (there are 20, one per AA) during a charging reaction.

Question 6

What is the first step in translation?

Answer 6

First, initiation factors bind the mRNA, the initiator tRNA, and the small ribosomal subunit. This makes the initiation complex.

Question 7

What is the second step in translation?

Answer 7

tRNA brings the amino acids to the polypeptide chain one by one until a stop codon is reached. This is powered by the hydrolysis of GTP.

Question 8

What is the third step in translation?

Answer 8

Termination. The release factor binds to the stop codon, which releases the polypeptide and ejects the tRNA.