The topic of genetics and epigenetics is fascinating and complex. Genes determine a lot about an animal, including their visible phenotype and performance. Gene-determined traits may become evident in the animal over time or in the animal’s offspring.
What is Epigenetics?
Adding to the complexity is ‘epigenetics‘. This includes factors in the environment, like food eaten or chemicals inhaled, that alter the effects of the genes without causing a change, or mutation, in the genes. When epigenetic changes turn the genes on or off, the appearance or function of the animal may change too. That epigenetic effect may appear only in the exposed individual (the F-0 generation), or in it’s offspring (the F-1 generation) as well. In some cases, the food eaten or the chemicals breathed can influence grandchildren (F-2) and even future generations never exposed to the food or chemicals that produced the epigenetic changes.
Epigenetics Research in Sheep
A study done at the University of Wisconsin -Madison used rams (F-0) fed a special diet that included methionine, an amino acid that sheep must eat to form proteins. The body cannot make methionine but sheep need it to produce proteins in wool, meat, milk and fetuses. Eating methionine led to chemical changes in cytosine, one of the four bases of DNA (along with adenine, guanine and thymine). The F-0 rams fed methionine and their F-1 offspring created from sperm of the F-0 ram maintained the same order of DNA base sequences. No mutation had occurred. However, they both had the same chemical change to their cytosine base in their DNA.
The rams’ grand-offspring (F-2) and future generations (F-3, etc) did not consume the feed containing higher levels of methionine. Even still, their DNA contained the same chemical change to cytosine that the F-0 and F-1 generations had. ‘Transgenerational epigenetic inheiritance’ (TEI) from F-0 to F-2 had occurred in the sheep. The F-2 grand-offspring rams had reduced scrotal circumference and loin muscle depth. The chemical change to cytosine appeared to have undesirable effects on the reproductive and growth traits of the sheep.
In genetics, what you see (the phenotype) may not be exactly what you have in the genotype, due to epigenetics. Are there epigenetic factors that could improve performance? Are epigenetic changes reversible? How do more distant generations fare? There is much more in the field of genetics and epigenetics to be discovered.