How Genetics Influence your Child’s Looks, Personality and Intelligence

While scientists have made quantum leaps in genetic research, we wondered what else they might have learned that affects what our children may inherit from us.

He’s got Mama’s eyes, Daddy’s smile and Aunt Edna’s earlobes. She’s got Grandpa’s button nose and looks just like you did as a baby. They’re just so beautiful that you sometimes wonder how in the world you created such a miracle. You might also wonder how your son got red hair when his parents are both brunettes, or if he’ll even keep his hair since all the men in your family are balding. Or if your daughter will be a sweet soprano like you or wind up tone deaf like her father.

Although scientists have decoded the human genome (the three billion “letters” or chemical building blocks that make up human genetic material), modern science is still years away from clearly understanding parental inheritance. Since doctors are first attempting to identify the genes that cause illnesses like cancer and Parkinson’s disease, the genes for eye color and athletic ability will remain a mystery for a while longer. But we’re not completely in the dark; and with the information we already know, we can make some pretty good guesses about our future NFL quarterbacks and Mozarts.

The Basics

Most cells in the body contain 46 chromosomes, but Dad’s sperm and Mom’s egg each contain just 23 chromosomes. When egg meets sperm, they join to form the 46 chromosomes of a single cell that will rapidly divide until it becomes the approximately 100 trillion squirming cells that you lovingly diaper, feed and babble to all day.

Each chromosome carries many genes, which also come in pairs. Since half of your baby’s genes come from mommy and the other half are from daddy, the probability of a baby getting any particular gene is similar to the probability of flipping a coin. Sounds like predicting the possible combinations that make up your baby’s looks and personality should be easy, right? No such luck. Only a few traits, such as blood type, are controlled by a single gene pair. Most traits, like skin color, hair color and height are the result of lots of genes working together, many of which are still unidentified.

Blue, Green, and In Between

“We know some factors influencing human pigmentation, including skin and eye color, but we definitely don’t understand this fully,” says Dr. Kathryn E. Beauregard, PhD, and deputy editor of The American Journal of Human Genetics. So can you predict eye color? Not exactly, but you can get close. Light-colored eyes like blue, gray and green are recessive and more likely to show up when both parents have light eyes and less likely to appear when one or both parents has brown eyes. But it is possible for two brown-eyed parents to have a blue-eyed child if the genetics are right.

Hair color follows the same basic principles as eye color. The degrees of darkness depend on the amount of melanin produced, with genes for less melanin (or lighter hair) being recessive and darker hair being dominant. What about those fiery redheads? Red hair results from a special recessive gene for red hair. When combined with genes for brown or black hair, the red gene is obscured and often goes unnoticed. But combined with genes for lighter hair shades, and you get strawberry blonds, light auburns and flaming orange carrot tops.

What about those with no hair at all? One popular misconception is that the mother’s side of the family passes along the gene for male pattern baldness. This belief has had men monitoring the scalps of their maternal grandfathers and uncles for years. In truth, baldness is a complicated genetic trait that can be inherited by either the mother, the father or both. So don’t blame your mom for hair loss!

Thoroughbred Jockey or Pro Wrestler

Height is another complicated trait that’s influenced not only by a child’s genetic makeup, but also by outside forces like health and nutrition. Gender plays a role as well, since boys tend to grow taller than girls. Scientists approximate that genetics and gender count for about 70 percent our height, while 30 percent is determined by environmental factors such as diet, exercise and overall health. Popeye was right when he extolled the virtues of spinach! Humans have been growing steadily taller over the centuries as our nutrition and health care improve.

For a fun and fairly accurate method to determine your baby’s adult height, add the parents’ heights together, divide by two, then add 3 inches for a boy or subtract 3 inches for a girl. While this method is relatively good, your child’s ultimate height can vary by as much as 5 inches above or below this calculation.

Mozart to Manilow

Although specific genes affecting musical ability have yet to be identified, there is undoubtedly a link between musical ability and heredity. In most cases, great musical talent shows up at a very young age, and great musicians usually have parents or close relatives with similar talent. But genes can’t do it alone. A child who inherits “musical genes” will rarely exhibit any talent without environmental stimulus like music played in the house, singing lessons or early exposure to musical instruments. The University of California San Francisco is currently conducting a study of people with perfect pitch. Their research shows that 40 percent of children who begin formal musical training by age four develop perfect pitch. In contrast, only four percent of those who began training after age nine did.

On the other hand, a person can be trained and coached to become a solid musician, but without the right DNA, will never become a virtuoso. UCSF scientists found that musicians with perfect pitch were four times more likely to report a family member with perfect pitch than those without it.

Smart Alecs and Alices

Like musical ability, research indicates that intelligence has both biological and environmental bases, but that genetics play a powerful role in intelligence potential. Studies show that the IQ difference between identical twins (even those raised in different homes) is miniscule (5.9 points), and many research studies indicate the more closely related two people are, the more similar their IQ’s are likely to be.

Although genetics have a lot to do with intelligence levels, environment has a lot to do with how those innate smarts actually develop. For example, a challenging environment may boost your IQ, but your score could drop again if your environment changes. Researchers in Canada found that baby rats whose mothers gave them more attention learned more easily, while doctors at UT Southwestern Medical Center at Dallas say spending time with your children, reading to them, playing games and otherwise showing you care not only makes your children feel good, but it could help them be smarter.

What about so called “genius genes”? Science sees genius as a rare combination of superior genes, which may not even require a high level education to flourish. Two of history’s greatest minds, Leonardo de Vinci (sculptor, mathematician, engineer, artist, musician and poet) and William Shakespeare came from obscure backgrounds and had very little formal education. Despite lack of flashcards and preschool classes, both displayed dazzling intelligence and talent from the time they were young children.

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