Abstract
Bovine mitochondria contain a 16338 nucleotide closed loop of
DNA coding for 13 translated genes, 22 tRNA and 2 rRNA and is
inherited exclusively through the maternal line, providing a genetic
mechanism for cytoplasmic inheritance. Several early analyses
of cattle populations indicating significant cytoplasmic variance
in production traits were criticized on statistical grounds.
Analysis under an animal model has revealed significant effects
on milk fat concentration in two studies with Holsteins, but not
in two other studies and no significant effects were found for
growth and lactation traits in two beef cattle studies. Studies
relating dairy performance to mitochondrial nucleotide variation
across previously analyzed mitochondrial lineages found significant
associations, but do not provide an independent test of mitochondrial
effects. In a separate population no associations were found.
The evidence is broadly consistent with 0 to 5% of variation
in performance due to cytoplasmic effects, with the weight of
evidence pointing to the low end of this range. If at the upper
end of this range, however, cytoplasmic effects could be of practical
importance.
1Animal Science, Iowa State University