New Babies: Genetic Reflections of Generations Past

The birth of a baby is often a blissful and exciting time in the life of a family. Proud parents and grandparents beam at the bundle of joy, awed at the creation of a new generation of their family. The time surrounding a birth is filled with family bonding, as the now-grandparents teach the new parents what they learned in their own journeys as mothers and fathers.

Part of the fun that a growing family has during this time is deciphering where the new baby got each of his or her features. Comments such as "She has her mother’s eyes" or "He has his father’s nose" are commonly heard at social events and family get-togethers. Bit by bit, a baby is pored over, with this characteristic being attributed to this parent and that feature being attributed to that parent.

Matching an infant’s features with his or her parents’ features isn’t always so clear-cut, however. In my own family, for example, my parents, sister, and I all have straight, brown hair and brown or green eyes. My brother, on the other hand, has curly, blond hair and blue eyes. Looking at the five of us, one might think that my brother belongs to a different family. Many of his physical characteristics cannot be attributed to either our mother or our father. But, if you could take a step back and look at the bigger picture--the bigger family portrait--you would see that my brother has the same physical characteristics as our maternal grandmother and many of our cousins on our mother’s side. The curly, blond hair and blue eyes become commonalities when you look at the family as a whole.

A baby inherits physical characteristics from his or her parents. The vehicle of this inheritance is DNA (deoxyribonucleic acid), which carries traits such as facial features and hair color from one generation to the next. When a baby is conceived, a zygote is formed from the mother’s egg cell, which contains one-half of the mother’s DNA, and the father’s sperm cell, which contains one-half of the father’s DNA. The resulting child receives half of his or her genetic makeup from the mother (through the egg cell) and half from the father (through the sperm cell).

Likewise, the baby’s parents inherited their DNA from their mothers and fathers. This means that the physical characteristics of the baby’s grandparents can be reflected in the features of the baby. If you think about my brother again, this helps explain how he resembles our maternal grandmother. Some of our grandmother’s DNA was passed through our mother to my brother.

Just as DNA can be used to understand the inheritance of a baby’s physical features, it can be used to determine or verify a baby’s relationships to various family members. Paternity testing is one common example of this application of DNA. A paternity test is a DNA test that compares a child’s genetic profile with an alleged father’s genetic profile to determine whether the alleged father is truly the biological father of the child. (Remember: The child inherited half of his or her DNA from the father, so their profiles should have at least a 50% similarity.) Another common application of DNA is called grandparent DNA testing or grandparentage testing, which determines whether two alleged grandparents are the biological grandparents of a child. There are a number of similar tests that can be performed to help people understand or confirm their various family relationships.

It should be noted here that family relationship DNA testing is different from DNA testing for physical characteristics. The results of family relationship DNA tests reveal whether or not the tested individuals are biologically related; these tests are not used to predict the inheritance of physical traits.

The next time you look at a newborn baby and contemplate where he got his wavy hair or where she got her rosy cheeks, remember that his or her DNA has been traveling through the generations--distributing physical features from parent to child--for years. DNA is the link that connects a family’s newest addition to its great-great-grandparents and beyond.

Visit GrandparentageTesting.com for more information about paternity testing, grandparent DNA testing, and other DNA tests that can be used to verify your family relationships.