How Does Genetics Influence Height?


The Role of DNA

A person’s height is determined primarily by genetic factors, as a research shows that height basically is an inherited trait. While some parents may worry that a child’s short stature may be caused by an underlying health problem, doctors now are able to use DNA as a fairly accurate predictor of height. Although health, nutrition, and whether a woman smokes during her pregnancy each can influence a child’s growth rate, there are several different genes that determine height in the end. A mix of genes coded for bone development, growth hormones, and metabolic enzymes all play a part in normal growth and development.

Predicting a Child’s Height

The height of a child’s parents in inches can be used to predict height as an adult. The gender of the parent plays into the formula as well. In most populations of the world, adult males on average tend to be taller than adult females. For male children the height of the mother is added to the height of the father, plus 5 inches, the total of which then is divided by two. For female children, the height of the mother is added to the height of the father, again calculated in inches. However, five inches are subtracted from the total, divided by two. This should be a fairly decent predictor of a child’s approximate height in adulthood, give or take an inch or two. It also supports the notion that family members are likely to be of similar stature. Doubling a child’s height at age two is another close predictor, as a child normally reaches half of his or her adult height by that time.

Delayed Growth Patterns

Parents must keep in mind, though, that some children grow more slowly than others do. If this is the case, it’s a good bet that at least one of the parent’s was a slow developer, too. Many children who appear to be small for their ages actually are growing at a normal rate. The problem may be delayed bone age, which means that their skeletal age is younger than a child’s chronologic age. This condition, know as constitutional growth delay, often is the case when no other symptoms of disease are present. While these children tend to reach puberty at an older age than their peers, their bodies catch up by the time they reach adult height. They simply continue to grow until an older age. In most cases, the child’s parents usually were “late-bloomers” as well.

Other Factors Affecting Growth

A deficiency of growth hormones can cause a delay in a child’s growth. In this case, the pituitary gland at the base of the brain is not producing enough hormones for normal growth. The thyroid gland, another organ of the endocrine system, may not secrete enough thyroid hormone, which is needed for bones to develop normally. This condition, known as hypothyroidism or underactive thyroid can cause serious problems in a child’s growth and development if left untreated. Genetic abnormalities such as Down syndrome, a chromosomal disorder, can stunt a child’s growth as well. Turner syndrome is a common genetic disorder affecting normal growth and development. Occurring in female children only, there is a missing X chromosome, causing the child to experience slower growth and delayed puberty, with the most common feature being short stature.

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