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| home : pages : what's new in medicine vol. 2 : microsort in sex : | |||||
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MICROSORT IN SEXIf your dream is to have a daughter, then this technology is for you...MicroSort has been used in cattle for more than a decade. The machine for sorting sperm in farm animals was developed by Lawrence Johnson, a scientist at the Department of Agriculture. Female sperm in all animals have more genetic material than male sperm, mean-ing they are larger. Johnson's flow cytom-eter first dyes the sperm and then passes them through a narrow opening. As they shuffled along they are zapped with an ultraviolet laser. The X-bearing sperm glow brighter and the machine uses that difference to sort X from Y. The flow cytometer has been used in the birth of more than 400 animals, including sheep, pigs, and cows. The offspring born of the method appear normal, as do the subsequent generations. To be used on humans, the flow cytometer had to be tuned, since the gap between the size of X and Y bearing sperm is far smaller than in animals, and therefore more difficult to sort. The only currently recognizable dis-tinction between living X and Y bearing spermatozoa is their total DNA content, owing to the larger size of the X chromo-some. The first successful separation of human X-and Y-bearing sperm cells based on the 2.8% total DNA content difference using FCS (Flow cytometric separation) was reported by Johnson and the team from the Genetics & IVF Institute in Fairfax, VA. Sperm identified with one distinct red spot were classified as haploid X chromosome-bearing cells, and those with the distinct green spot as haploid Y chromosomes. The first birth of normal daughters after MicroSort sperm separation was reported by F. Fugger in Human Reproduction vol 13, 1998 (the journal published by the European Fertility Society). , Indications for MicroSort X separation are prevention of sex-linked disorders (for women who are carriers of X-linked disorders) and family balancing (when you already have one or more male MicroSort may by followed by 1U1, WE or ICSI to achieve pregnancy. Most of the pregnancies were achieved after simple IUI. 92.9% of the pregnancies were solely of the desired female gender. All children born were healthy. The ability to separate X- and Y-bearing sperm cells provides new opportunities for women who are carriers of X linked disorders (hemophilia, Duchenne muscular dystrophy, X linked hydrocephalus). In most cases, the X-linked diseases are only expressed in the male offspring of carrier mothers. The use of MicroSort for the enrichment of the X-chromosome bearing sperm cells can now allow for the preferential conception of unaffected female offspring. Concerns regarding the use of ultraviolet light and the dye Bisbenzimide for FCS of human sperm have been expressed (Ash wood-Smith 1994) Bisbenzimide is a non cyto-toxic DNA stain which binds to a minor external part of DNA according to Dr. Fugger, the head of the Cryobank in Fairfax, VA. Pregnancies have also been attained with the use of frozen sorted sperm cells. --> return to menu / back ... (click) --> return to top of the page (click) |
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