Use of PGD to Avoid Affected Children in Couples Carrying Dominant Genetic Traits for Disease

Preimplantation genetic diagnosis (PGD) is beneficial to couples who carry dominant genetic traits and wish to avoid having affected children.

UNDERSTANDING DOMINANT GENETIC TRAITS

Family health history plays an important role in the health of a child. An individual has two copies of nearly every gene, one from each parent. Changes, or mutations, in a gene, interferes with the way it works and can cause disease.

Dominant genetic mutations are mutations that are present in only one copy of that particular gene. That means a parent that has a dominant mutated gene can pass the trait on to a child. If one parent has an autosomal dominant disorder, each child they conceive will have a 50 percent chance of inheriting that disease. Spontaneous mutations can also occur in individuals with no family history of the disease.

Autosomes are non-sex determining genes. Examples of autosomal dominant diseases include Huntington’s disease, neurofibromatosis, achondroplasia and familial hypercholesterolemia.

X-linked dominant diseases occur as a result of mutated genes located on the X chromosome. Males have only one X chromosome, so both dominant and recessive mutated genes on the X- chromosome will cause disease in males. Often, both males and females in each generation will be affected in families that have X-linked dominant disorders.

EXAMPLES OF DOMINANT DISORDERS

There are numerous genetic traits that can be identified through PGD. Some examples of dominant genetic disorders include Huntington’s disease, Marfan’s syndrome, achondroplasia (a type of dwarfism), some types of glaucoma, and polydactyly (extra fingers or toes).

WHO IS A CANDIDATE FOR PGD?

Individuals who have, or who are a risk for having, a specific disease that could be passed on to their child are advised to consider PGD. Preimplantation genetic diagnosis may be beneficial for couples undergoing IVF, increasing the chances that only healthy embryos are transferred.

HOW PGD IS PERFORMED

Embryo biopsy is typically performed on day five and six. Testing is safe and does not cause harm to the embryo.

A few cells are removed and tested for genetic abnormalities. The results are used to determine which embryo(s) are appropriate for transfer. Typically, embryos with normal test results and morphology are eligible for transfer.