A genetic carrier screening aims to identify which autosomal recessive pathologies an individual carries. In the case of women, also identify X-linked diseases.
It is estimated that we all carry recessive diseases. However, in most cases, having a recessive pathology has no clinical consequences for the individual. That is why we do not know which pathologies we carry.
The likelihood of an individual carrying a recessive condition varies depending on the condition. In our population, some of the pathologies in which the frequency of carriers is highest are Cystic Fibrosis (1 in 36 people are carriers) or Spinal Muscular Atrophy (1 in 40 people are).
Autosomal recessive diseases are those in which the two copies of the gene (the copy inherited from the father and the one inherited from the mother) need to be altered to develop the disease. When only one copy of the gene is altered, the individual is a carrier of that condition.
A couple is at risk of transmitting an autosomal recessive pathology to their offspring when they are carriers of the same pathology. In this case, your child has a 25% risk of inheriting the disease, a 50% risk of being healthy as a parent and a 25% risk of being healthy and not a carrier.
X-linked diseases are those in which the gene responsible is on the X chromosome. Women having two X chromosomes are carriers of the disease but men, being XY, develop the disease.
When a woman carries an X-linked disease, her daughters have a 50% risk of being carriers and their sons have a 50% risk of inheriting the disease. In some cases, women may present with clinical manifestations associated with the pathology. This is because one of the random X chromosomes is inactivated in each of the cells.
It is made from DNA obtained from a peripheral blood sample. This sample sequences the genes associated with the recessive genetic diseases included in the study.
Carrier genetic screenings are an option for those couples who want to reduce the risk of their child developing a recessive disease.
Dra. Belen Garcia. Genetic counselor at FIVclínic.