Find Information About:

Drugs & Supplements

Get information and reviews on prescription drugs, over-the-counter medications, vitamins, and supplements. Search by name or medical condition.

Pill Identifier

Pill Identifier

Having trouble identifying your pills?

Enter the shape, color, or imprint of your prescription or OTC drug. Our pill identification tool will display pictures that you can compare to your pill.

Get Started
My Medicine

My Medicine

Save your medicine, check interactions, sign up for FDA alerts, create family profiles and more.

Get Started

WebMD Health Experts and Community

Talk to health experts and other people like you in WebMD's Communities. It's a safe forum where you can create or participate in support groups and discussions about health topics that interest you.

  • Second Opinion

    Second Opinion

    Read expert perspectives on popular health topics.

  • Community


    Connect with people like you, and get expert guidance on living a healthy life.

Got a health question? Get answers provided by leading organizations, doctors, and experts.

Get Answers

Sign up to receive WebMD's award-winning content delivered to your inbox.

Sign Up

Children's Health

Font Size

Genetic Scientists Put Down's Syndrome on the Map


The German- and Japanese-led team that mapped both chromosomes is also part of the Human Genome Project, an international effort to break the chemical codes of the entire human genetic blueprint. Humans are normally born with 23 pairs of different chromosomes, which are made up of genes.

Chromosome 21 contains relatively few genes, but they are in a complex tangle.

"When one stares at a sequence like this, it makes you realize how complex it really is," says Huntington F. Willard, PhD, chairman of genetics at Case Western Reserve University in Cleveland. He was not involved in the research.

"It's not just a simple string of 225 genes. It's really a mess, a hornet's nest -- a hodgepodge of duplications, altered sequences, and arrangements that determine the health and welfare of our species."

Reeves tells WebMD that this new information, combined with what is now known about chromosome 22, hints that humans may have only half of the 70,000 or 100,000 genes that scientists had speculated.

"To have the [chromosome] 21 consortium announce that there were only 225 genes is quite a surprise," Reeves adds. "In addition, they went another step and combined their information with that from chromosome 22, and they projected there may be only 40,000 human genes in all."

The researchers found that chromosome 21 contains far fewer genes than the 545 in chromosome 22, the second-smallest chromosome.

The map of chromosome 21 is 99.7% complete; technical limitations prevented a complete mapping, says Patterson.

Rudolph Tanzi, a professor of neurology at Harvard Medical School, said the chromosome map could eventually shed light on why people with Down's syndrome have very low rates of breast, lung, and gastrointestinal cancers. It could be that an extra copy of chromosome 21 has tumor-suppressing qualities.

"One can argue that an extra dose of a gene will usually be a bad thing, but once in a while it can be a good thing. It can be protective," Tanzi said.

The Human Genome Project expects to have a rough draft of the entire human genetic blueprint done this summer. The public project, which is expected to finish its work by 2003, is competing against a private company, Celera Genomics Corp., of Rockville, Md., which hopes to sell the information to pharmaceutical companies and others.

1 | 2

Today on WebMD

child with red rash on cheeks
What’s that rash?
plate of fruit and veggies
How healthy is your child’s diet?
smiling baby
Treating diarrhea, fever and more.
Middle school band practice
Understanding your child’s changing body.

worried kid
jennifer aniston
Measles virus
sick child

Child with adhd
rl with friends
Syringes and graph illustration