Single-nucleotide polymorphisms (SNPs) arise from "point mutations"
Sequence variation in a portion of the mtDNA cytochrome b genes from three species of North American deer

Mule    5'-ttc ggc tct ctg cta gga att tgc tta atc cta caa aat ctt act-3'
Deer        F   G   S   L   L   G   I   C   L   I   L   Q   N   L   T

Caribou 5'-ttt ggc tct cta cta gga atc tgc tta att cta caa atc ctt acc-3'
            F   G   S   L   L   G   I   C   L   I   L   Q   I   L   T

Moose   5'-ttc ggt tct cta tta gga gtt tgc tta atc tta caa atc ctt aca-3'
            F   G   S   L   L   G   V   C   L   I   L   Q   I   L   T

[ The sense strand is shown. Amino acids are in the single-letter code: the mtDNA genetic code differs from the "universal" code. ]

Interchanges of pyrimidine (c t) or purine (a g) bases are transitions (Ts)
Exchanges of pyrimidine for purine (pyr pur) bases are transversions (Tv)

Note numerous third-position polymorphisms in all sequences:
        note more complex pattern at last position ( a c t)

Note second-position transversion (t a) in the Mule Deer, resulting in an isoleucine asparagine  (I N)  substitution.

Note first-position purine transition (a g) in the Moose, resulting in an isoleucine valine (I V) substitution.

Note synonymous first-position pyrimidine transitions in leu (L) codons of Moose

Text material © 2012 by Steven M. Carr