What is a genome and how much does my genome (DNA sequence) differ from my neighbors?
There are four letters in the DNA sequence of all living things: A, T, G and C. Your genome consists of linear strings, or chromosomes, totaling 3 billion of these same four letters. Your genome is 99.9% identical to the genome of any other person anywhere in the world. All humans have the same genes, but in 1 out of every 1,000 letters there is likely to be a difference; some individuals may have a T at a given position while others have a G.
