Inheritance means that we get certain of our traits, our physical appearance, and some of our mental abilities from our parents. We say that these things are passed on to us from our mother and father through their genes. Of course, we can’t always tell specifically what we inherited from one parent or the other, but we have learned a good deal about some inherited things. For example, if a child’s mother has blood that is type A, and the father has type B, then the child will have type A or type B blood. He will not have type 0 or type AB because he has not inherited the genes for those blood types from either parent.
Physical traits or characteristics such as eye color, hair color, and other things, are inherited according to Mendel’s law, This means we can often tell In advance whether a child will have blue or brown eyes, or will turn out to be a blond or a brunette.
It is thought that highly intelligent people are more likely to have highly intelligent children than are people of normal or lower intelligence. This is not always true because, once in a while, highly intelligent people become ineffective parents, and less bright people become excellent parents. In other words, the way a child is brought up may be more important than the kind of brain he inherits. It is possible that “highly intelligent” people may be so busy with their own interests that they pay too little attention to their children, or they spoil their children by giving in to them too often. Thus a child who has inherited exceptional genes may not turn out well. On the other hand, parents who admit that they are not terribly bright themselves may spend a great deal of time teaching their children and encouraging them to learn, and those children may turn out better than the ones who inherited such good 1 genes.
Some of the most common inherited traits are the color of our skin, the color of our eyes, the color of our hair, our height, our blood type, and our general appearance. We realize though that our mother and father may not look very much alike. Therefore, if the mother has blue eyes and the father has brown eyes, we might inherit either blue or brown eyes. If they both have brown eyes, then, of course, we are more likely to have brown eyes. Frequently, a very tall man will marry a very short woman. Then their children can turn out to be short, or medium, or tall. But if a tall man marries and has children with a tall woman, then most of their children will be tall. And, if a short man marries and has children with a short woman, then most of their children will be short.
A good number of illnesses and defects are carried through the genes and can be inherited. Fortunately, many of the genes causing defects or diseases are recessive genes. This means that they are not very strong, and either may not have any influence on a child or may cause defects or disease only once in a very rare while.
In the past twenty or thirty years, doctors have studied inherited defects and diseases very carefully in order to prevent as many of them as possible. They have found that some conditions can be treated successfully by special medicines and diets. They have also found that giving the proper advice to people before they have children may prevent children from being born with an inherited disease or defect. For example, if a man with diabetes marries a woman with diabetes, the chances are that most of their children will develop diabetes. And if a man with a blood condition known as a positive sickle- cell trait marries a woman with the same positive sickle-cell trait, most of their children will develop a disease called sickle-cell anemia. To prevent this situation, the men and women who carry these genes may be advised to adopt children rather than to have them naturally. And we know that adopted children can be just as fine and wonderful as the children parents have themselves.
Most inherited detects in newborns don’t amount to much, such as an extra toe or extra finger, or even an extra nipple. These can be removed easily by a surgeon and the child will be as normal as can be.
Nature is really wonderful, because most newborn children are perfect. Ninety-seven out of a hundred newborn babies are absolutely perfectly formed, and most of the defects in the other three children are not serious. A lot of them, like an extra toe or an extra nipple, can be corrected easily by surgery. The saddest defects are the ones in which the child’s mind has not developed properly. But even among this small group of mentally handicapped children, we now know a great deal about how to make their lives happy. And, luckily, mental defects are not inherited very often, unless there are mentally handicapped people in both the mother’s and the father’s family.