Changes in the DNA are reflected in the protein product. There is a correlation between what happens to the genetic sequence and the resulting protein sequence.
Three DNA nucleotides form a codon and specifiy amino acids.
As represented by this huge stack of paper, the human genome contains more than three billion nucleotides or DNA "letters."
Synthesizing human insulin using recombinant DNA, 3D animation with no audio
Fred Sanger outlines DNA sequencing.
Because it contains the directions for assembling the components of the cell, DNA is often thought of as the "instruction book" for assembling life.
DNA has four "letters" that must specify the 20 different amino acids that make up proteins. Combinatorially, using three DNA letters for one amino acid makes the most sense.
A human is a complicated organism, and it is considered unethical to do many kinds of experiments on human subjects. For these reasons, biologists often use simpler “model” organisms that are easy to keep and manipulate in the laboratory.
Gene analysis take a giant leap using DNA sequencing.
Erwin Chargaff was the first to accurately measure nucleotide amounts in DNA.