Most people remember from life science or sex education courses how a baby’s sex is determined: The combination of two X chromosomes during fertilization will result in a female being born; the union of an X chromosome with a Y will produce a male.

Much to the chagrin of men, there are several genetic deficiencies associated with the Y chromosome. X chromosomes tend to appear in pairs, and have a mechanism for eliminating undesirable genes by passing the most errorless chromosome on to the zygote. Y chromosomes, however, travel alone and have no such mechanism for the reduction of bad genes.

Enter Dr. Bruce Lahn, a University of Chicago professor of genetics, whose research on the Y chromosome has uncovered some saving graces for the paternal parent. While the Y chromosome contains many useless genes, it also includes some important ones, which control such functions as male fertility.

Some may also be interested to read Lahn’s research on a possible pill that would reduce the probability of giving birth to a genetically flawed male child.

Lahn, however, is most interested in why the Y chromosome has changed both function and form over millions of years. Among his contributions to the field is his work identifying a gene apparently associated with the size of the cerebral cortex. Lahn recently wrote an article published in Nature Genetics that explores how the impact of sexual competition among males is visible at the molecular level.

Lahn, who first studied at Harvard and MIT, said he prefers the diversity of the Hyde Park community to the racial homogeneity of Cambridge.