The Sod1c polymorphism has a G to A transition at position 231 changing codon 77, within a positively charged amino acid domain of the Zinc subloop, from glutamate to lysine. The isoelectric focusing point is calculated to be 6.85 instead of 6.50. CuZn SOD activity in whole brain homogenates is 11% less in Sod1c homozygotes than in Sod1a homozygotes, and heterozygotes have in intermediate level of activity. No abnormal phenotype has been detected. This polymorphism is useful as a genetic marker.
The Sod1c allele was backcrossed from the strain SOD1/EiJ onto the C57BL/6J background by Charles Epstein at UCSF. In 2000 homozygous females at backcross generation N10 and homozygous males at either backcross generation N10 or N11 were shipped to Muriel Davisson at The Jackson Laboratory and this strain was sibling inbred from that point on until 2005 when embryos were generated for cryopreservation by in vitro fertilization using C57BL/6J females and homozygous males at generation N10+F11.