Nucleic Acids 6

Question 1

What is the nature of the genetic code ?

Answer 1

1. Non-overlapping- each nucleotide is part of only one triplet
2. Degenerate- multiple codons can code for the same amino acid
3. Almost universal- the letters used are always the same in all organisms

Question 2

What is an open reading frame ?

Answer 2

The region between an initiation codon (AUG) and a termination codon

Question 3

Describe the features of tRNA

Answer 3

1. Small: 73-90 nucleotides long
2. Contain some unusual bases. Eg. Thymine, dihydrouracil etc.
3. All tRNAs have an anticodon
4. All have the unpaired sequence CCA at their 3’ end
5. Clover leaf secondary structure

Question 4

What are aminoacyl tRNAs ?

Answer 4

tRNAs attatched to their amino acids

Question 5

What is base wobble ?

Answer 5

The ability of some bases at 5’ end of anticodon to pair with more than one base at the 3’ end of codon.
This means some tRNAs can recognise more than one codon

Question 6

What is the enzyme that links tRNAs to amino acids ?

Answer 6

Aminoacyl-tRNA synthetase
There are 20 different types, one for each of the different amino acids