Explain why there must be three bases in each code.

The question refers to the genetic code used in DNA and RNA, which is based on a sequence of three nucleotide bases - also known as a codon. Here's why there must be three bases in each code:

1. Information Storage: DNA and RNA store genetic information in the form of a sequence of nucleotide bases. There are four different bases in DNA (adenine, cytosine, guanine, and thymine) and in RNA (adenine, cytosine, guanine, and uracil).

2. Coding for Amino Acids: This genetic information is used to produce proteins, which are made up of a sequence of amino acids. There are 20 different types of amino acids that can be used in a protein.

3. Need for Variety: If each codon consisted of only one base, then we could only code for four different amino acids. If each codon consisted of two bases, we could code for 16 different amino acids (4^2). However, because there are 20 different amino acids, we need at least three bases per codon, which allows for 64 different combinations (4^3), more than enough to code for all 20 amino acids.

4. Redundancy and Error Prevention: The fact that there are more combinations than necessary allows for some redundancy in the genetic code. This means that even if a mistake is made in one of the bases, it may still code for the correct amino acid, preventing errors in protein synthesis.

5. Start and Stop Signals: Additionally, some of the 64 possible codons are used as 'start' and 'stop' signals for protein synthesis. This wouldn't be possible if we only had enough codons for the 20 amino acids.

So, the use of three bases in each codon is a result of the need to code for a large number of amino acids, provide redundancy to prevent errors, and signal the start and end of protein synthesis.