Because there are four naturally occurring nitrogenous bases, there are four different types of DNA nucleotides ... these determinations is learning the nucleotide sequences of the DNA segments ...

Base substitutions are the simplest type of gene-level mutation, and they involve the swapping of one nucleotide for another during DNA replication. For example, during replication, a thymine ...

Thousands of single changes in the nucleotides that make up the human genome have been associated with an increased risk of developing cancer.