According to a new research in monkeys, they provide compelling evidence that DNA, particularly a type inherited only from the mother, plays an important role in determining a newborn's birth weight. Based on genetic analysis of six generations of macaque monkeys, a team led by Dr. James C. Ha at the University of Washington in Seattle assessed that genes account for 45% of the inconsistency in birth weight.
The research also indicated that DNA in the cytoplasm--the jelly-like substance that surrounds the nucleus in each cell--was responsible for about 11% of the variability in birth weight among the study animals. According to a report, this is the first time that researchers have been able to demonstrate a link between cytoplasmic DNA and birth weight. The results suggest that a mother's genes may have a particularly large influence on birth weight, since genetic material in cell powerhouses called mitochondria, which are found in the cytoplasm, are inherited only from the mother.
Many factors are known to influence birth weight, such as nutrition, smoking, drug use and stress, but according to Ha, the results suggest that birth weight "is a function of an interaction between our DNA and our environment." Of course, the study was carried out in monkeys, not humans, but Ha said he has no reason to doubt that DNA plays a similar role in people.
In fact, a study published earlier this year found that while women smokers were more likely to have a low birth weight baby, the odds were greatest among women with certain genetic make-ups. Environmental factors like maternal smoking certainly play key roles in birth weight. But the knowledge that genes also help determine a newborn's weight could have implications for preventing low birth weight, Ha said, since the effects of environmental factors may vary depending on a person's genes.