Why are there nucleotides (a, t, g, and c) in the master mix? what are the other components of the master mix, and what are their functions?

Nucleotides are the monomers used for DNA synthesis. The mix also contains a template, DNA taq polymerase, buffer, reverse and foward primer and magnesium ions.

Explanation:

A PCR master mix is a premixed solution that has all of the components for a Polymerase chain reaction (PCR). This reaction is a laboratory technique that amplifies small fragments of DNA into millions of copies.

The master mix used for that contains dNTPs (nucleotides). In the DNA there are four types of nucleotides that are differentiated by the nitrogen base they have: adenine (A), guanine (G), cytosine (C) and thymine (T).

Since nucleotides are the monomers that make DNA, they are found in the mix because they are the material for DNA synthesis.

The reaction mixture also requires;

the cell theory states that all living things including animals, as well as plants, are made of cells.