American Medical Association Family Medical Guide - American Medical Association [23]
• Hemoglobin carries oxygen in red blood cells and gives the cells their red color.
• Hormones control a variety of biological processes, such as growth, sexual development, and the activities of some organs.
Genetics: The future of medicine
You will one day be able to learn from your unique genome what disorders you are at increased risk of developing, which will enable you to take steps to prevent them. Doctors will be able to prescribe drugs that are more precisely tailored to your individual genome. They would know, for example, what medication or combination of medications for high blood pressure would be most effective for you.
Eventually, scientists hope to find the genes that enable some people to live to 100 or older. Using the information they glean from the genes, they will be able to devise new treatments, drugs, special vitamin formulas, or even combinations of foods that could enhance the activity of the genes and increase healthy life expectancy for everyone—even those of us who were not born with the life-prolonging forms of these genes.
How Genes Are Transmitted
Your genes are continuously being copied inside your cells in a process of cell division called mitosis. Mitosis occurs thousands of times every second to make new cells to replace damaged, dying, or dead cells. Egg and sperm cells are different from other cells in the body and divide in a process called meiosis. Each egg or sperm cell contains half the DNA of body cells, and each is genetically unique. An egg and sperm combine at conception to form a cell with a full set of genes, half from each parent. This random mix of genetic information accounts for the limitless variety of people in the world.
The cycle of life
Genetic Testing
As you read and hear more and more about genetic testing, you may want to consider being tested for a condition that seems to run in your family. You may want to learn if you carry genes that increase your risk of developing a particular disorder later in life or of transmitting a severe, life-threatening genetic disorder to a child. For many diseases that are inherited through a single gene or pair of genes, tests are available to detect the genes in people who carry them, often from a simple blood test. The odds of passing one of these so-called single-gene disorders to offspring can be calculated relatively easily. However, for other diseases, the risks are more difficult to define, and the best course to follow is not always clear. To be able to make informed decisions, you will need to understand the implications the information has for you personally. For information about genetic counseling, see page 952.
Gene chips
Studying a person’s DNA from a small sample of his or her blood or saliva, scientists can detect a wide variety of genes that increase susceptibility to particular disorders. A genetic analysis is made by reading a person’s DNA on a gene chip.
The Dangers of Smoking
Cigarette smoking is the major cause of preventable death in the US, causing nearly half a million premature deaths each year. The smoke from a cigarette contains more than 4,000 chemicals—at least 60 of them known to cause cancer. Nicotine, the substance in tobacco that makes smoking highly addictive, raises your heart rate, irritates the lining of your blood vessels, and promotes blood clotting, increasing your risk of heart attack and stroke. The carbon monoxide in cigarette smoke reduces the level of oxygen in your blood.
Smoking causes nearly nine out of ten cases of lung cancer—the No. 1 cancer killer of both men and women—and causes other cancers, including cancer of the mouth, throat, esophagus, bladder, kidneys, cervix, and pancreas. Smoking is also responsible for most cases of emphysema and chronic bronchitis and is a major risk factor for heart disease, the leading cause of death in both men and women. Women over age 35 who both smoke and take birth-control pills increase their risk of having a heart attack or stroke.
Why You’re Hooked
Researchers have discovered