Introduction to translation

Question 1

Define translation

Answer 1

Translation is the mRNA-directed biosynthesis of polypeptides.

Question 2

Explain how a DNA base sequence might specify an amino acid sequence in many ways

Answer 2

There are only 4 bases that code for 20 amino acids, so a group of several bases (codon) is necessary to specify a single amino acid.

Question 3

What is the minimum number of bases required per codon and why

Answer 3

The minimum number of bases per codon is 3 - 4 to the 3 is 64 different triplets of bases whereas 4 to the 2 is only 16 different doublets- this is insufficient to specify all the amino acids.

Question 4

What does it mean when we say that the genetic code is degenerate (redundant)

Answer 4

It means that amino acids can be specified by more than one codon.

Question 5

Describe the genetic code

Answer 5

The genetic code is a nonoverlapping, comma-free, degenerate triplet code.

Question 6

If you are given alternating sequences of 3nt (UAC) poly, how many reading frames are there

Answer 6

There are 3 reading frames and 3 different peptides can be obtained

Question 7

Can ribosomes initiate polypeptide synthesis in any reading frame?

Answer 7

Yes

Question 8

Which direction is mRNA read by a ribosome?

Answer 8

5’-3’

Question 9

What are stop codons

Answer 9

Also called nonsense codons because they do not specify amino acids but instead signal the ribosome to terminate polypeptide synthesis.

Question 10

What is AUG or GUG

Answer 10

Chain initiation codons that specify the amino acid residues Met and Val