A) Citrate synthase (CS) activity was measured as described in Materials and Methods. There was a trend in which CS activity was 29% and 17% increased in the heterozygotes and the Cox7a1 knockouts, respectively. However, differences were not statistically significant (p=0.13 WT-HT; p=0.27, WT-KO) (n=4). B) Ndufb6 gene expression was measured by qPCR as described. *, p<0.05. C) MtDNA content of Cox7a1+/+, Cox7a1+/- and Cox7a1-/- was determined by qPCR as described in Materials and Methods, relative to a single copy nuclear gene (mouse β-2 microglobulin) using total DNA.