8.1 Genes and the genetic code

Question 1

What is a gene

Answer 1

A section of DNA that codes for a polypeptide

Question 2

What is the coded information in the form of

Answer 2

Specific sequences of bases along the DNA molecule

Question 3

What is a lcus

Answer 3

The position of a gene on a DNA molecule

Question 4

What is the minimum number of bases that code for an amino acid

Answer 4

3

Question 5

Why did scientists believe that only 3 bases was the minimum for coding an amino acid

Answer 5

Only 20 different amino acids, a pair is only 16 and three makes 64 which is more than enough

Question 6

What are the features of the genetic code

Answer 6

1. A few amino acids are coded for by a single triplet
2. The remaining are coded for by between two and six triplets each
3. The code is known as ‘degenerate’ because most amino acids are coded for by more than one triplet
4. A triplet is read in one direction
5. The start of a DNA sequence is always the same triplet. If it doesnt form part of the final polypeptide its removed
6. Three triplets code for stop codons, three triplets code for no amino acid
7. The code is non-overlapping, each base is read once.
8. The code is universal, each triplet codes for the same amino acid in ALL organisms

Question 7

What are exons

Answer 7

Sequences of bases that code for amino acids

Question 8

What are introns

Answer 8

Sequences of bases that dont code for amino acids