Maternal Effects: Genes are not all you mother gives you

Gregor Mendel, an Austrian monk, is credited with discovering the basic principles of genetics in the 1860s and known as the father of genetics. According to his results, the two parents contribute one set of genes each, which forms the genotype (genetic makeup) of the child. The genotype expresses itself in the physical characteristics (called phenotype) of the individual.

However, the study of inheritance has time and time again been proven to be much more complex than Mendel thought it was. It has been found that non-genetic environmental factors influencing the parent can cause a change in phenotype of the offspring. This is studied under a whole new field called epigenetics.

For example, any pregnant woman can testify to the fact that advice is everywhere- what she should eat, how she should sit and stand, even how she should feel. And why wouldn’t they be? Research has shown that the lifestyle of a woman during pregnancy affects the child’s overall health. If the child was only to be influenced by the mother’s DNA, these correlations would not exist. These are what we call maternal effects.

Flickr Creative Commons image.

Flickr Creative Commons image.

Maternal effects are the phenotypic (observable) changes that occur in a child due to maternal influences other than genetic inheritance.  The food she eats while she is pregnant changes the environment that the fetus is growing in.  Environmental effects cover a broad range of factors- some influence maternal effects, while others influence the offspring directly. Epigenetic changes in the mother’s genome during her lifetime can result in changes in the phenotype of her future child. Note that epigenetic changes are those changes in the genome that do not concern the DNA sequence. Rather, these are external factors that determine whether certain genes will express themselves or not.

A lot of studies relating to maternal effects have taken place on birds as well. One  is a study on canaries about the effects on carotenoids in the mother’s diet on her children. Carotenoids are certain pigments most animals cannot synthesize and must obtain from plants in the diet. A study showed that if a mother’s diet was rich and carotenoids, the benefits like better growth and increased cell immunity were found in the children, sometimes without the offspring having carotenoids in their own diet.

Flickr Creative Commons image.

Flickr Creative Commons image.

In the same way a lot of studies have been done on humans- a mother who is pregnant is advised to take care of her nutrition intake, the amount of toxins she ingests, monitor her stress levels, and exercise properly.  This has been shown to have a correlation to the child’s cardiovascular health.  For example a recent study showed that children of mothers who were pregnant during the Chinese famine (i.e. were malnourished) had high mean systolic blood pressures as adults. This was more prevalent in children whose mothers were already suffering from hypertension previously in their life.

Another study done on the effects of children whose parents went through the Dutch famine also yielded some fascinating results. The earlier the fetus was in its developmental stage, if it was conceived during the famine, the more adverse were the effects on its health. What is strange is that the health effects occurred much later in the life of the offspring: they weren’t born small, but had poor cardiovascular health as adults. Researchers believe this implies that surviving the hostile uterine environment may have taken certain adaptations. The maternal effect here, say researchers, is the hostile uterine environment. In order for a fetus to have survived that, they would have had to make certain adaptation. However, those adaptations may have cost them coronary heart disease later in life.

The study of maternal effects has great implications in the study of evolution. Sometimes, mother organisms can adapt to (or become better at adapting to) certain environmental changes. They transmit these traits to their offspring via non-genetic factors and thus increase the survival rate of the species. Maternal effects form a vast and fairly unchartered territory in the field of genetics, and hold great prospects for genetics, ecology and evolutionary biology.

About the Author

Sunishka “Sonny” Thakur is a sophomore majoring in Genetics. She channels her passion for science, literacy and world culture through campus involvement in women in science, UGA Science Olympiad Outreach, First Book UGA and World Ambassadors. She can be reached via email: sunishka.thakur25@uga.edu. More from Sunishka Thakur