Cytogenetics

What is cytogenetics?

Cytogenetics is the study of chromosomes. Specifically, their structure, function and how changes in chromosomes cause diseases.

Chromosomes are threadlike structures that organize your genes, which are made of DNA (the instructions for how your body works). You can think of a chromosome as a pearl necklace with genes being the pearls.

Changes in your chromosomes can lead to health conditions you’re born with. They can also cause cancer. Some changes cytogenetic testing can detect include:

• Aneuploidy: Having more or fewer than 46 chromosomes
• Deletions: Missing parts of one or more chromosomes
• Duplications: Added parts of one or more chromosomes
• Translocations/rearrangements: When part of a chromosome, or chromosomes, moves to an incorrect location

Why do cytogenetic changes happen?

Errors in cell copying can cause chromosome changes. If this happens during the creation of egg and sperm cells or during fetal development, you can be born with certain health conditions. Dividing cells can also cause chromosome changes during your lifetime, leading to cancer. Sometimes, you can inherit chromosome changes from your biological parents.

What is cytogenetic testing used for?

Cytogenetic testing can look for chromosomal differences:

• To diagnose or determine treatment options for certain cancers
• To diagnose genetic diseases before or after birth
• During preimplantation genetic testing as a part of IVF (in vitro fertilization)

Types

Types of cytogenetic tests include:

• Fluorescence in situ hybridization (FISH): This technique looks for specific pieces of chromosomes. It uses glowing labels to identify if a portion of a chromosome is present or not.
• Karyotyping (chromosome analysis): This technique organizes your chromosomes. It allows medical professionals and researchers to see your chromosomes under a microscope, count them, and determine their length and other features.
• Microarray analysis: This technique finds whole chromosome deletions or duplications, as well as partial chromosome deletions and duplications. It can also find those that are too small to be seen on a karyotype.

What happens during cytogenetic testing?

What you need to do for cytogenetic testing varies. It depends on what your healthcare provider is testing for. Your provider needs a sample of tissue, fluid or cells. They’ll send that to a lab for testing. Samples for testing could include:

• Amniotic fluid for prenatal testing
• Blood for children and adults
• Bone marrow or tumor tissue for cancer diagnosis or treatment
• Cells from embryos for preimplantation genetic testing (PGT-A)

How long does it take to get results of cytogenetic testing?

It can take anywhere from a few days to a few weeks to get your results. It depends on what the test is looking for. Ask your provider when to expect results.

What is the difference between genetics and cytogenetics?

Genetics is the study of genes and how we inherit them. Cytogenetics is the study of chromosomes and changes in them that cause disease.