SNPs(Single nucleotide polymorphisms)

# more than 99% of human DNA sequences are the same across the population

# it must occur in at least 1% of the population.

# SNPs, which make up about 90% of all human genetic variation, occur every 100 to 300 bases along the 3-billion-base human genome

# two of every three SNPs involve the replacement of cytosine (C) with thymine (T)

# SNPs can occur in both coding (gene) and noncoding regions of the genome.

# Many SNPs have no effect on cell function, but scientists believe others could predispose people to disease or influence their response to a drug