1. The triplet code Starter A DNA molecule is 23% guanine.
What percentage of each of the
other bases would it contain?
G = 23%
C + G = 46%
C = 23%
A = 27%
T = 27%
So A + T = 54%
(to make a total of 100%)

2. Aims:
What is a gene?
How do genes code for polypeptides?

3. A gene is a section of DNA nucleotides that codes for the sequence of amino acids that make up a particular polypeptide.

4. Depending on the specific groups in each amino acid the polypeptide chain then forms secondary & tertiary structures

5. The triplet code Only 20 amino acids
Each amino acid has its own code of bases on the DNA
3 bases code for an amino acid (triplet code)
64 codes so some amino acid have more than one code.
In eukaryotes much of the DNA doesn’t code for amino acids – introns
Sections of DNA that code for a.a - exons
Introns found between and in genes

6. Features of the triplet code
Few amino acids have only a single triplet code
Most have between 2-6 triplet codes each
Degenerate code
Always read in one direction
Start of a sequence is always the same triplet code – methionine
3 triplet codes are stop codons
Code is non-overlapping and universal

7. Understanding checkpoint
An enzyme is a protein that is responsible for speeding up chemical reactions. An enzyme’s shape is crucial to it’s function.
How would a change in one base result in an enzyme becoming non-functional?

18. Aims: Explain to your partner
What is a gene?
How do genes code for polypeptides?