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Sperm Donation to Avoid Passing on Genetic Diseases
a blog by Michelle Ottey, PhD, Director of Operations, Fairfax Cryobank and Cryogenic Laboratories, Inc., January 17, 2010
Genetic traits are passed in several ways: autosomal dominant, autosomal recessive, sex-linked or structural chromosome abnormalities. When considering having a child, knowing your genetics is important when there is a known risk factor.
Dominant Genetic Diseases
Dominant genetic diseases are caused by a mutation in one copy of a gene, and this means that a resulting child would have a 50 percent chance of inheriting the mutated copy of the gene from an affected father. Donor sperm is an alternative that rules out this risk.
Another option is to create embryos through in vitro fertilization (IVF) and have pre-implantation genetic diagnosis (PGD) done to identify non-carrying embryos to be transferred into the female partner.
Recessive Genetic Diseases
Recessive genetic diseases would be inherited by a child if both parents are carriers of the same recessive disease. If both parents are carriers, there is a 25 percent chance of a resulting child being affected, a 50 percent chance of the resulting child being a healthy carrier and a 25 percent chance that the child will not inherit the mutation from either parent.
If the male partner is the affected (dominant/recessive) or carrier (recessive), using a sperm donor would rule out the risk of passing a genetic disease on to the child. Or if the woman knows she is a carrier, then using a donor tested as a non-carrier, reduces her risk significantly for having an affected child.
Sex-Linked Genetic Diseases
For sex-linked genetic diseases that are linked to the Y-chromosome, an affected or carrier male partner would always pass the mutation on to a male child. For those diseases linked to the X-chromosome, an affected or carrier male would always pass the mutation on to a female child. Sex-linked diseases are a small set of diseases for which there may be testing available.
Sperm Donor Screening
All of our sperm donors have a karyotype or chromosome analysis done to screen for structural abnormalities that could manifest in a disorder or predispose to miscarriages. Our sperm donors are also tested for the most common genetic diseases that affect the general population, as well as for ethnically relevant diseases.