Professor Jus St. John
We analysed a number of characteristics, otherwise known as traits, in a population of pigs (total = 5687) that have an important bearing on the economic breeding value of each pig. We then determined the mitochondrial DNA background of each pig and classified it according to known mitochondrial DNA haplotypes. Mitochondrial DNA haplotypes are groupings or clusterings of mitochondrial sequences that indicate common maternal ancestral origins. We found associations between mitochondrial DNA haplotypes and fertility, fatness, muscle depth, fatness to leanness ratios, and lifetime daily gains in weight.
Mitochondrial DNA is different to nuclear DNA as we inherit it from our mothers only. It has long been thought that there are links between mtDNA haplotypes and certain diseases such as diabetes and cancer. Our study using a large cohort of pigs showed that over multiple generations mitochondrial DNA haplotypes can influence a number of traits and this is irrespective of the male breeding partner or the breed of pig. Most interestingly, our study also showed that there are 'genetic trade-offs' between the mitochondrial haplotypes and certain traits. For example, those haplotypes associated with good fat to leanness ratios were poorer performers for fertility, as they had poorer egg quality and smaller litter sizes, and vice versa. This indicates that mitochondrial DNA haplotypes are afforded an advantage in one respect but a disadvantage in another.
Centre for Cancer Research
Mitochondrial Genetics Group
Journal and article title
We were surprised to see such clearly defined 'genetic trade-offs' in our pig cohorts. This is usually very evident in experimental models used by evolutionary biologists but it is now also evident in large mammals.
Mitochondrial DNA haplotypes were often thought to influence health outcomes and certain performance criteria. The pig is regarded by many regulatory agencies, such as the pharmaceutical testing agencies, to be an important model to study the human as its organ sizes, physiology and embryology are more similar to the human than many other animal models. Although not stated in the paper, our work suggests that, if health providers wish to plan which resources they would provide in certain areas, they need not just to look at ethnicity but also the mitochondrial DNA haplotypes across that region. This will provide an indication of the susceptibility of the population to specific diseases or illnesses and ensure more effective planning.
Fertility, fatness, muscle depth, fatness to leanness ratios, and lifetime daily gains in weight.