Health matters ... the genetic ripple effect.
The behaviour and experiences of our parents and grandparents can affect the traits they pass on to us, new research reveals.
A phenomenon called epigenetics shows how environmental influences can flick the switch on genes that might otherwise remain switched off.
We each have around 25,000 genes - which contain information telling the body's cells what to do - but, not all our genes are active, or expressed, at any one time. Epigenetics (which means above the gene) is the study of changes in gene activity that can be inherited, but do not involve alterations to the genetic code.
So while we might inherit a set of genes, what we eat or experience emotionally can influence which of those genes are activated. This biological imprint can then be passed on to our children.
Studies increasingly show that nutrients, toxins, prenatal or postnatal environmental exposures can suppress or activate a gene. This can affect everything from our emotional wellbeing to our susceptibility to disease. Certain genes, for instance, when switched on can suppress cancer.
Back in the beginning of "the noughties", a study of mice by Duke University found that "even subtle changes in maternal nutrition can dramatically change the coat colour of the offspring and their susceptibility to diseases like obesity, diabetes, and cancer by simply altering the epigenome."
Of the study, lead researcher Randy Jirtle said: "For the first time ever, we have shown precisely how nutritional supplementation to the mother can permanently alter gene expression in her offspring without altering the genes themselves."
Now, scientists at The Victor Chang Institute in Sydney have taken those findings a step further. In the study, the mother's diet determined whether a gene that controls the colour and likelihood of obesity, as well as its tendency to overeat, was switched on or off in the offspring.
"We've been giving [nutritional] supplements to [mice] mothers mid-gestation, when the ovaries and testes of the embryo are forming," says Dr Catherine Suter. "So, we've been targeting the next generation. We found influences are stronger in second generation than first - there's [some kind of] memory of what your mother or grandmother ate."
Suter says that the mice used in the study were genetically identical. Changes in appearance and health of the offspring were simply the result of different diets.
"We've been working in this space for awhile now," she said. "We know that poor [maternal] nutrition can lead to early onset disease later in life [in the offspring].
"Now what's more pertinent is over-nutrition - something like 1 in 3 kids in primary school are overweight. There are inter-generational cycles of obesity - inherited complications - and it's not just about eating habits or whatever.
"What if you do eat well, [but] you have [weight] problems anyway?"
Epigenetics is helping to answer this question and helping scientists understand how to reverse the effects of previous generations' behaviour.
Unlike genes, which can take hundreds of years to change, epigenetic changes can occur relatively quickly.
"We don't need genetic change," Suter says. "It takes one generation [of dietary change] to revert."
Environmental influences also play a part.
Studies have found that the offspring of stressed male rats had significantly higher levels of depression and anxiety, The Wall Street Journal reported. Yet, it was also found that maternal care could result in pups that were "essentially normal."
Of this, Randy Jirtle says, "[The] rat studies show that maternal nurturing of the offspring after birth reduces their response to stress by altering the epigenome in the brain."
"There's some evolutionary mechanism to do with climate, nutrition and stress that we react to," says Suter.
Scientists are still learning the rules of epigenetics and how to selectively target genes. But, it demonstrates how dynamic we are. We are not just lumped with what we've got.
Epigenetic regulation also occurs in the mature, fully developed brain. There is, therefore, the potential to adjust our behaviour and affect the way our genes operate.
"An individual [may] be at higher risk of adult-onset disease," says Suter. "But 'risk' is key here - it is not a fait accompli. Being mindful of that risk and living a healthy lifestyle may ameliorate that programming to some extent. Also, if that programmed risk is reduced then the intergenerational cycle of increased risk will eventually be broken."