I think that the HGP can be compared only to the project that took the man to the moon. Before continuing, let me tell you a few facts about genes and its malfunctions. Strictly speaking a gene is a DNA sequence composed of four chemicals known as nucleotides which are Adenine, Thymine, Cytosine and Guanine, however they usually, tough not correctly, referred to as bases and abbreviated as A, T, C and G, respectively.
Genes vary in length and sequence according to the protein they code for.
They are the instructions for the cell to synthesize proteins. A process also known as gene expression. Gene expression is controlled through the interactions of specific DNA sequences with specific protein factors. Each gene has its own control sequences . You can think of those sequences as switches that are turned on or off by the protein factors, thus allowing the gene to be expressed or not.