3. The Genetic Code

Define what a gene is:

A specific sequence of bases on DNA which codes for a specific sequence of amino acids in a polypeptide chain

What is the first word we use to describe he genetic code?

a triplet code

What is meant by ‘triplet code’?

3 bases codes for 1 amino acid

Describe the nature of the Genetic Code

• Non- overlapping

• Degenerate

• Universal 

Is the genetic code overlapping or non- overlapping?

Non- overlapping

What is meant by non- overlapping?

Successive triplets are read in order.

Each nucleotide is part of only one triplet code

What is meant by the term degenerate?

There is more than 1 triplet code for each amino acid.

What is meant by universal?

The code is the same for all species which allows us to determine evolutionary history

Explain how the genetic code can be described.

It is a triplet code. Each triplet code is discrete. Each triplet code codes for 1 amino acid. It is universal and degenerate/ non- overlapping.

During translation how can you identify where one polypeptide starts?

The codon AUG both codes for methionine and serves as an initiation site: the first AUG in an mRNA's coding region is where translation into protein begin.

During translation how can you identify where one polypeptide ends?

In the genetic code, a stop codon (or termination codon) is a nucleotide triplet within messenger RNA that signals a termination of translation