After nearly a decade of painstaking work, Stanford University researchers have determined the entire genetic sequence of individual human sperm - a breakthrough that could shed more light on infertility and many other disorders.
Though the first whole-genome sequence of somatic cells was deciphered in 2003 itself, this is for the first time that sperm cells have been sequenced.
The human gametes or sex cells namely, sperms and eggs are different from somatic cells (body cells). While the sex cells are haploid containing only 23 chromosomes, body cells are diploid and have 46 chromosomes.
Sperm cell contains a random mix of the father's parents' genes and the egg cell contains a random mix of the mother's parents' genes. A natural process called recombination ensures that a baby is a blend of DNA from all four of his or her grandparents.
To sequence the entire genome of the human sperm cell, researchers Jianbin Wang, Stephen Quake and Barry Behr first isolated sperm cells from the semen of the study subject who was a 40-year-old man. The genome of each sperm was sequenced separately. His whole-genome sequence (obtained from diploid cells) has been previously sequenced to a high level of accuracy.
Until now, scientists had to rely on genetic studies of populations to estimate how frequently recombination had occurred in individual sperm and egg cells, and how much genetic mixing that entailed. But in the Stanford study, by comparing the sequence of the haploid sperm with that of the diploid cells, scientists were able to locate where each recombination event took place.
According to the researchers, the single-sperm sequencing could serve as a new kind of early detection system for men who may have reproductive problems, and one day, with other, correlating features could be used to harmlessly identify healthy sperm for use in IVF (In Vitro Fertilization).
The study is published in the July 20, 2012 edition of the journal Cell.
by RTT Staff Writer
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