Heredity and the Growth Spurt

The internal clock. As you have learned, every cell in your body contains chromosomes, which determine your physical and mental capacities. From your knowledge of heredity, you know that these characteristics were passed on to you by your parents and that neither you nor they can change them. These chromosomes act as a sort of internal clock that sets the time when you will have an adult physique, or body build.

This internal clock controls the beginning of your growth spurt, the rate of your growth, and the time when it will end. It even times the growth of the parts of your body.

You can blame it if your feet get too large or your nose too long. In fact, this clock also helps to determine your body build, athletic capabilities, and a great deal of your personality.

The chromosomes in your internal clock determine all these characteristics only if other factors do not interfere. Your chromosomes might influence your body to grow tall. If you had very poor nutrition, however, you would not grow as tall as you could have. Nutrition, exercise, diseases, and other factors can change the plans of your internal clock.

Predicting size and build. If you look carefully at your parents, you can probably detect many similarities between them and you. However, it is not very often that a person has all or most of his parents’ traits. It is most likely that you will inherit some traits from one parent and some traits from the other.

Because your size is largely determined by your inheritance, you may be able to get a rough idea of your size at maturity by looking at your parents. However, this method is not always accurate. A short mother not a tall father can have tall, medium, and short children. Because of the peculiar way chromosomes work parents of medium height may have tall children, short children, and any size between. Look at the chart to see how parents’ heights affect their children.

Your bone structure, weight, and physical appearance are determined in the same way as your height. However, each of these characteristics is more complex than height. Consequently, it is not likely that you will look exactly like your parents in any of these ways. However, you may have many similar characteristics. Prediction of these characteristics is extremely difficult even in the best of circumstances.

Severe growth problems. If you think that you have serious growth problems, it would be wise to see your doctor. You will remember that the parathyroids, pituitary, and other endocrines control your skeletal growth and physical development. Occasionally, these glands may secrete too much or too little of the hormones that control growth. Doctors can treat this glandular problem by reducing the activity of the gland or by giving regular doses of the necessary hormones. You must realize, however, that there are only a very few cases of glandular difficulty. Most teenagers’ growth problems are not based on glandular problems and can be solved by several relatively simple methods.

Try This

Take two or three of your outstanding physical characteristics and trace them back to your grandparents. Are all your outstanding traits inherited from one side of your family?