Last But Not Least

Scientists have completed the first sequencing of a woman's DNA. (Four male genomes have already been sequenced, the first in 2001.) The DNA belongs to Dr. Marjolein Kriek, a clinical geneticist at Leiden University Medical Centre. Professor Gert-Jan B van Ommen, leader of the team working on the project says, "If anyone could properly consider the ramifications of knowing his or her sequence, it is a clinical geneticist." The sequence mapping or decoding is important, van Ommen says, because, "While women don't have a Y-chromosome, they have two X-chromosomes. As the X-chromosome is present as a single copy in half the population, the males, it has undergone a harsher selection in human evolution." It must be noted, however, that before scientists mapped a female genome, they sequenced the DNA of about a dozen mammals, including chimpanzees, dogs, cats, cows and a platypus. [Time, Science Daily]