Frequently Asked Questions: Clinical Genetics

Frequently Asked Questions: Clinical Genetics

What are genetic diseases?

Genetic
diseases are caused due to change in DNA sequence apart from normal. It may be
due to change in one gene (single gene disorders), multiple genes (multigenic
disorders), interaction between genes and environment (multifactorial
diseases), or change in structure or number of chromosomes. With progress in
science, we are learning that almost every disease may have direct or indirect
genetic basis.

Are genetic diseases always inherited from parents?

No. In some diseases like thalassemia, parents carry gene with mutation which is inherited by the affected baby. But in some diseases, mutation in the gene may be new or spontaneous even if parents do not have it (such as achondroplasia), or may occur later (like in cancers).

How will learning about genetic diseases help us in prevention?

We knew that
some common diseases like diabetes, heart disease, asthma, cancers run in
families. Also rare diseases like thalassemia, sickle cell anemia, metabolic
diseases run in families. Depending on the disease, prevention can start from
preconceptional counseling to prenatal diagnosis and if diagnosed later early
intervention can result in better outcome.

What is genetic testing and where can it be done?

Genetic testing, also known as DNA testing, is used to examine and identify any changes in genes, chromosomes, and proteins. It includes various tests like newborn screening, chromosome testing, mutation analysis, prenatal tissue or sample testing etc. It involves specialized laboratory expertise and interpretation of the result. 

Types of
genetic testing:

• Diagnostic testing – to confirm diagnosis of genetic
  disorders
• Presymptomatic testing – to identify at risk individuals
  of conditions such as cancer who can be helped by treatment   
• Carrier testing – in cases of family history of a
  genetic disorder
• Pharmacogenomics – to determine the appropriate
  medication and dosage for a particular condition
• Prenatal testing – to detect genetic abnormalities in
  the unborn child during pregnancy
• Newborn screening – to detect some genetic
  abnormalities in the newborns
• Preimplantation testing – to screen the embryos for
  genetic abnormalities before in vitro fertilization (IVF)

How is genetic testing done?

Genetic
testing is done by obtaining samples of blood or tissue etc. In pregnant women,
amniotic fluid (through amniocentesis) or the tissue of placenta (through
chorionic villus sampling) can be obtained as samples.

When is the genetic testing required?

A clinical geneticist is the right person to recommend what test is required and what can be done once the test results are obtained, which is an important step in the process of genetic diagnosis and management.