Making it in a Tough Environment -- You and Your Genes!

Where did
you get
your pairs
of genes?

You got your 70,000 pairs of genes when your dad's sperm pierced your mom's egg. One gene from each pair of your mother's 70,000 pairs of genes was already waiting in the human egg. Your father's sperm added one gene from each of his 70,000 pairs of genes. Your father's and your mother's genes paired with each other inside that fertilized egg cell from which you then grew.

The original egg cell split and re-split, forming new cells for muscle, brain, skin, bone and all the rest of your body. These new cells came together (according to the genes' orders) and each new cell carried copies of the original cell's genes. The result: Two copies (a pair) of about 70,000 genes are found in each of the 100 trillion or so cells of your body. (That's a lotza mozzarella!)

The mix of genes you each got from your parents directs your growth to adulthood and old age. When you have children, you, in turn, pass a copy of one or the other of each pair of your genes to each of your kids - but not always the same one of the pair. Your husband or wife will do the same. Each child is very likely to get a different mix and be different from the others.

Even brothers and sisters (unless they are identical twins) don't get the same mix of genes from their parents. So, although they may have similar noses or hair or height, their bodies in other ways will be different and may react differently - less or more - to the sun, to tobacco, alcohol, or to some chemicals in bug killers or other products at home, school, or work.

Getting features from our parents

is called our heredity, the sum of our genes. But our genes alone will not determine all things, like size. A child who is sick for a long time or doesn't eat well, for example, may not grow as tall as his or her parents.

The reverse can happen, too. Good nutrition, clean air and water, vaccines, and simple hand washing can prevent diseases and help a kid soar above shorter parents.

In such ways, the substances you touch and breathe, and your personal habits and nutrition play important roles. Along with your genes, the good and bad things in your world help decide who you are, how you feel and whether you get sick or stay well.

Proteins -- not just beans and a big, juicy steak, but a key to all life!

There are thousands of proteins, each made up, in part, of nitrogen, the colorless gas that makes up most of our air. Proteins are found in animal muscle (steak) and skin, bone and all the "stuff" of life, every cell of an animal or plant. They are also what make the body work: They are necessary for the chemical reactions that make muscles flex, brains think, and stomachs produce digestive fluids.

Think of genes as the orders or plans for a house. (This house could be your body, your dog 's body or your petunia plant.) Picture the proteins as not only the nuts and bolts, plaster and concrete, wood beams and floors, but also as the workers that create and assemble these things and set the furnace and lights and gas stove to working.

The Gene's Code for Life

While the English language has 26 letters, each gene's orders, or instructions, are written in a chemical code of four. The code is made up of chemical bases called adenine, thymine, guanine and cytosine. We call these A, T, G and C - the gene code's four letters. Long lines, or sequences, of these chemicals permit each of the 70,000 or so genes to have a different code that directs the making of a different protein. One gene = one code = one protein. The proteins carry out the gene's instructions.

Some 'Tyypos' (typos)
Along the Way

Mistakes can occur as the code is copied and re-copied when the cells divide. A substance in our environment can sometimes make a mistake occur or prevent it from being corrected by the body's "spell check." Sometimes this doesn't matter much, but sometimes it matters a lot.

Cells

One mipslaced (misplaced!) letter

in the long-strung code of one gene can cause sickle cell anemia -- a painful disorder in which the red blood cells have an odd shape like a sickle or crescent moon, instead of being round. The sickle shape makes it hard for the blood cells to get around in the blood vessels.

Another disease that is inherited in this direct way is cystic fibrosis. This is a disease in which mucus clogs the lungs.

How small are your genes?

When you stuff yourself into a pair of tight jeans, think about how your 70,000 gene pairs are stuffed by the thousands into 23 pairs of long capsules called chromosomes -- which are in every one of our cells. Even chromosomes are invisible to the naked eye. When these paired chromosomes have been stained, however, they can be seen under a very good magnifying microscope.

Here 's some trivia that could win a prize on a TV quiz: "Chromo" is a Greek word for "color" or "stain," and "some" (rhymes with "home") is Greek for "body."

Most diseases have a non-gene trigger.

Unlike cystic fibrosis and sickle cell anemia, most diseases and disorders are not caused just by "bad" genes but by bad genes along with one or more "bad" things from the world around us. One scientist makes it very simple: Heredity loads the gun and environment pulls the trigger!

Here's an example: When you were just born, you were tested for a genetic disease that is influenced by your environment - in this case, what you eat. That disease is PKU, in which protein is not eliminated but builds up.

If protein foods are eaten, the brain will not fully develop. (One artificial sweetener has a warning that it contains this protein and should not be used by people with PKU.)

While some cancers, heart disease and diabetes run in families and may be due to "bad" genes, other things are at work too. Our environment, our care in using chemical products, our personal habits, and our diet and exercise can be important. Did you eat your broccoli today? Drink your orange juice? (Eating at least five fruits and vegetables a day appears to reduce our risk of cancer!)

Links Disclaimer and Caution
When you encounter this image or the words "Non-NIEHS Link", it means that by following that link you will be leaving the NIEHS website. NIEHS is NOT responsible for non-NIEHS websites. Sites maintained by outside organizations may be changed without notice to NIEHS. Therefore, unless the link is to another U.S. government sponsored webpage, endorsement by NIEHS is not implied, and NIEHS does not guarantee their continuing safe content or privacy policies. So please ask your parent or guardian before continuing to any non-NIEHS website, and especially before providing any information via the internet or by e-mail. When last reviewed, the websites linked from the NIEHS Kids' Pages seemed suitable for you to visit, but that may have changed; if you have any difficulties or concerns with any linked materials, please let us know.

Links Disclaimer and Caution

When you encounter this image link to a non-NIEHS site

or the words "Non-NIEHS Link", it means that by following that link you will be leaving the NIEHS website. NIEHS is NOT responsible for non-NIEHS websites. Sites maintained by outside organizations may be changed without notice to NIEHS. Therefore, unless the link is to another U.S. government sponsored webpage, endorsement by NIEHS is not implied, and NIEHS does not guarantee their continuing safe content or privacy policies. So please ask your parent or guardian before continuing to any non-NIEHS website, and especially before providing any information via the internet or by e-mail. When last reviewed, the websites linked from the NIEHS Kids' Pages seemed suitable for you to visit, but that may have changed; if you have any difficulties or concerns with any linked materials, please let us know.