Humans seem to have accelerated the pace of just about everything from communication to climate change, but the rate of our genetic mutation remains slow and steady.

New research, published online today in Current Biology, compared the same Y chromosome DNA sequence of about 10 million nucleotides in two men separated by 13 generations. The two men had a common ancestor that lived in the early 1800s. After analyzing the men's selected genetic sequences, the researchers found only four true genetic mutations. From that, they were able to calculate a steady rate of mutation for most people.

"These four mutations gave us the exact mutation rate—one in 30 million nucleotides each generation—that we had expected," Chris Tyler-Smith, of the U.K.'s Wellcome Trust Sanger Institute and a co-author on the study, said in a prepared statement. These numbers amount to an average of 100 to 200 genetic mutations per person.

Continue Reading >

Inbreeding is the source of jokes about British royalty and is associated with increased birth defects among offspring. The practice is so reviled that 31 U.S. states ban marriage between first cousins or allow it only if the couple has undergone genetic counseling or at least one partner is sterile or no longer fertile because of age.

But those laws "seem ill-advised" and "should be repealed," a geneticist and medical historian write in today's PLoS Biology. "Neither the scientific nor social assumptions that informed them are any longer defensible."

The US "cousin marriage" prohibition stretches back to the 1858, when Kansas barred such marriages; Texas was the most recent state to pass a ban, in 2005, write Diane Paul, a political scientist emeritus at the University of Massachusetts, Boston, and Hamish Spencer, head of zoology at the University of Otago in New Zealand. (European countries didn’t ban the practice because there, "the rich and noble were marrying" their cousins, Spencer tells us. "In America it was immigrants and the rural poor — a much easier target of legislation than your monarch.")

Continue Reading >

Prenatal genetic tests such as amniocentesis (drawing some amniotic fluid from around a 16-week fetus) always carries a small risk of miscarriage. Now, a partnership between a group of Chinese researchers and a San Diego biotech company may result in a simple no-risk blood test that detects defects caused by single-gene mutations.

Chinese University of Hong Kong scientists report in the Proceedings of the National Academy of Sciences that they devised a technique that locates a fetus's DNA molecules in blood samples taken from its mother. The fetal DNA or genetic material, which tends to be shorter than that of the mom, is duplicated and subjected to a “molecular counting” technique that tallies both mutant and normal genetic material.  The new method overcomes what had been the major obstacle to such testing: distinguishing fetal DNA inherited from mom from mom's own DNA,

Continue Reading >