If all the cells in my body have the same DNA, then why don't all my cells look the same?

-A curious adult from California

March 27, 2004

This is a great question! As you probably already know, all of the cells in your body started from a single cell.

That single cell then divided many, many times to turn into the 50 trillion or so cells that make up you. Almost all of the cells in your body share the same DNA as was found in that first cell*.

So if they have exactly the same DNA, why are eyes and lungs so different? The answer lies with what DNA is and how it works.

What is a chromosome?

-A curious adult from California

March 20, 2004

A chromosome is DNA all scrunched up so that it fits inside a cell. DNA is the molecule that contains the recipe for creating and maintaining a living organism. The DNA in one of the trillions of human cells would be about 6 feet long if it were all stretched out.

Most people aren't even six feet tall, and cells are so small, scientists need a microscope to see them. In order to fit inside a cell, the DNA gets wound around special proteins that act like spools.

Is it possible for two brown eyed people to have a child with blue eyes? Both of these people have one parent with blue eyes,and one parent with brown eyes. Can brown-eyed parents have a blue-eyed baby?

-An undergraduate from Tennessee and a curious adult from Ohio March 13, 2004 The short answer is that brown-eyed parents can have kids with brown, blue or virtually any other color eyes. Eye color is very complicated and involves many genes. To begin to understand how parents with brown eyes could have blue-eyed children, let's imagine that eye color is due to a single gene, EYCL3, which comes in two versions or alleles, brown (B) and blue (b).

Please tell me if DNA can be taken from nail and hair clippings. Is it possible to determine if one is a Cohane (priestly tribe of the Jews)? How long does the whole process take and what would it cost and where do they do it?

April 1, 2004

The bottom line is you can get DNA from hair clippings but you cannot determine if a person might be a Cohane unless the hair was pulled out and includes the root. This is because the only DNA you can usually get from hair clippings without the root is mitochondrial, which, besides only coming from your mother, is not the DNA that can at this time identify someone as a possible Cohane.

Blushing From Alcohol

Why is Anne blushing? Find out how genetics can explain why some people turn red when they drink alcohol.

Are you a Super Taster?

Are You a Supertaster?

Some people think broccoli tastes unbearably bitter, and ice cream tastes sickeningly sweet, and lemonade tastes painfully sour. These people are supertasters.

Genes on Board

Why would Vikings need extra iron in their blood?

People with hemochromatosis absorb too much iron from their food. Everyone needs iron—it helps blood do its job. But absorbing too much iron damages the heart, liver, and other organs. People with this disorder must have their blood drawn periodically to keep from getting sick.