Some women give birth to babies with higher birth weights. Weight infants may be influenced by nutrition, maternal health conditions, and also because the gene. The scientists found that birth weight infants affected gene variation of mothers and grandmothers, but the influence of genes from the father is very minimal.
Previous researchers have learned that the gene acts as a growth suppressor that can reduce birth weight. But a British study found that certain genes passed down from mother to infant birth weight increased to 93 grams. Added weight can reach 155 grams if derived by the maternal grandmother.
In an article published in American Journal of Human Genetics, Professor Gudrun Moore of the University College London and colleagues examined a gene called PHLDA2 of 9500 DNA samples from the mother and baby. These samples were collected from three separate studies. Researchers discover gene variant called RS1 can alter gene function resulting in higher birth weight infants.
"Genes do have a huge effect on birth weight by acting as a growth suppressor. We found a genetic variant PHLDA2 derived from the mother can cause the baby to be born 93 grams heavier on average. Even its weight can reach 155 grams on average larger average if it is inherited by the maternal grandmother, "says Prof. Moore as reported by BBC News, Friday (23/03/2012).
RS1 gene variation is found in approximately 13% of individuals studied. While the S2 gene variations as much as 87%. RS2 gene variation is more common and this variation is only found in humans. The variation of the gene RS1 and RS2 are making babies are born smaller.
Researchers suspect that this mechanism is a protective effect to enhance the survival of mothers when giving birth. This means that birth weight is not too heavy will ensure mothers survive childbirth.
"Although this study only look at birth weight infants, it is likely that these genetic variants have long term effects on health. Health effects are partly due to the influence of birth weight and partly due to genetic factors," said Dr Caroline Relton from Newcastle University.
Newborns generally have an average weight of 3500 grams with a body length of 48-51 cm and the average head circumference 35 cm. The study also found that the influence of genes from father to infant birth weight is almost nonexistent.
"The genes of the father is less involved in the evolution. Perhaps because his own father's survival is at stake and can continue to reproduce with another woman," said Professor Moore.