Sperm's Genetic Blueprint Compiled: Analysis Uses Sex Cells to Calculate Human Mutation Rates

Article excerpt

Some scientists really throw themselves into their research, but Stanford biophysicist Stephen Quake has taken the all-in approach to a whole new level.

Using his sperm, Quake and colleagues compiled the first-ever genetic blueprint for a single sperm cell. The results shed light on molecular processes such as mutation and recombination in humans, the scientists report in the July 20 Cell.

Determining how often mistakes in copying DNA results in mutations to single DNA units is important for various reasons, including figuring out how long ago humans diverged from other species, says Laure Segurel, an evolutionary geneticist at the University of Chicago. "Every calculation is based on this mutation rate," she says.

In past studies, scientists estimated this rate either by comparing human DNA with that of other species to see how many changes occurred since that species split from humans, or by studying families to see where children have different DNA than their parents. For individual sperm cells, Quake and colleagues calculate the human mutation rate at 2 to 4 changes per 100 million DNA units per generation. That is higher than the rate calculated by looking at families, but consistent with evolutionary estimates.

The new work also offers insights into how humans scramble their DNA so that children inherit different combinations of parental DNA. …