Chromosomes

Scientists have found genetic evidence for what some men have long suspected: It is dangerous to make assumptions about women. The key is the X chromosome, the feminine sex chromosome that all men and women have in common. In a study published today in the journal Nature, scientists said they had found an unexpectedly large genetic variation on the X chromosome among women.

Whenever a couple of curious kids play a behind-the-woodshed game of doctor, they discover that male and female bodies are different. Later, they learn that nature designed masculine and feminine organs for particular functions, although the specifics can be confusing even for adults. Roseanne Barr says husbands think a uterus is a tracking device. Why else would they ask their wives to locate a milk carton hiding in plain sight in the refrigerator?

Scientists have completed the final analysis of two more human chromosomes. Chromosome 19 with nearly 1,500 genes, including some linked to high cholesterol and insulin-resistant diabetes, is the most gene-dense of those sequenced. By contrast, chromosome 13 has one of the lowest concentrations of genes with only 633. But they include the BRCA2 gene linked to breast cancer and others linked to bipolar disorder and schizophrenia.

In scientific circles, the Y chromosome -- the essence of masculinity -- is scorned as the runt of the human genetic family, so henpecked by mutations that it is wasting away. So little respect does this small, self-absorbed chromosome command that scientists investigating the human genome felt free to jeer or mostly ignore it -- until now. In research made public Wednesday, scientists confessed that they have sorely misjudged this single-minded sex specialist.

Japanese scientists said Friday they had built an artificial chromosome, which might aid efforts to use gene therapy to treat diseases such as muscular dystrophy and cystic fibrosis. Hiroshi Masumoto of Nagoya University in Japan and colleagues said they hope their chromosome might be used to deliver some form of gene therapy. Every human cell contains 46 chromosomes. These, in turn, carry the genes. Everyone has some "defective" genes, but some defects have more serious effects than others.

Girls are more socially adept than boys because they have the right genes, British researchers report in the June 12 Nature. Research on girls with Turner's syndrome showed a genetic link with social ability, they said. Healthy girls get one X chromosome from each parent, but girls with Turner's have only one good X chromosome. The team tested 80 girls with Turner's for social skills.

Small defects in the male chromosome may be responsible for some cases of infertility, University of Minnesota doctors report in the New England Journal of Medicine. Dr. Jon Pryor and his team found that 7% of the 200 infertile men they studied were missing tiny pieces of their Y chromosomes, genetic material found only in males. However, further study revealed that the deleted pieces did not always cause infertility.

In a major milestone in the study of human heredity, researchers announced Monday that they have created the first artificial human chromosome, which experts said represents a quantum leap in the ability to probe the complex molecules that make up humankind. The new technology offers scientists a powerful new research tool for investigating fundamental questions about the chemistry responsible for human heredity, experts said.

Kaposi's sarcoma, the once-rare form of cancer that has become a hallmark of AIDS, is characterized by specific chromosomal breaks that may be useful in early identification of the disease, according to researchers from the National Cancer Institute. Molecular biologist Nicholas C. Popescu and his colleagues report in the April 3 Journal of the National Cancer Institute that the tumors have specific deletions in the so-called short arm of Chromosome 3, similar to breaks observed in other tumors.

Every man on Earth today is related, linked by a Y chromosome to a common ancestor who lived about 190,000 years ago, a study suggests. This so-called ancestral Adam was among many males who lived before anatomically modern humans evolved, but he's the only one purported in the study to have a genetic legacy that persists today.