What Is a Karyotype Test?
A karyotype is a photograph of the chromosomes in a cell. Karyotypes can be taken from blood cells, fetal skin cells (from amniotic fluid or the placenta), or bone marrow cells. 1
Conditions Diagnosed With a Karyotype Test
Karyotypes can be used to screen for and confirm chromosomal abnormalities such as Down's syndrome and Cat Eye Syndrome, and there are several different types of abnormalities which may be detected.
When It's Done
There are many situations in which a karyotype may be recommended by your healthcare provider. These might include: 6
Steps Involved
A karyotype test may sound like a simple blood test, which makes many people wonder why it takes so long to get the results. This test is actually quite complex after collection. Let's take a look at these steps so you can understand what is happening during the time you are waiting for the test.
1. Sample Collection
The first step in performing a karyotype is to collect a sample. In newborns, a blood sample containing red blood cells, white blood cells, serum, and other fluids is collected. A karyotype will be done on the white blood cells which are actively dividing (a state known as mitosis).
2. Transport to the Laboratory
Karyotypes are performed in a specific laboratory called a cytogenetics lab––a lab which studies chromosomes. Not all hospitals have cytogenetics labs. If your hospital or medical facility doesn’t have its own cytogenetics laboratory, the test sample will be sent to a lab that specializes in karyotype analysis.
3. Separating the Cells
In order to analyze chromosomes, the sample must contain cells that are actively dividing. In blood, the white blood cells actively divide. Most fetal cells actively divide as well. Once the sample reaches the cytogenetics lab, the non-dividing cells are separated from the dividing cells using special chemicals. 8
Overview
A karyotype test uses blood or body fluids to analyze your chromosomes. Chromosomes are the parts of our cells that contain genes, which consist of DNA. You inherit genes from your parents. Genes determine your traits, such as eye and skin color.
Test Details
Most people don’t need to do anything to prepare for a karyotyping test. If you have had recent blood transfusions, be sure to ask your healthcare provider if you need to wait before doing the test.
Results and Follow-Up
You may need to wait a few weeks for the result of your karyotype test, though it could take more or less time. Ask your healthcare provider about when you can expect your results.
Procedure
The whole process of cell culture and harvesting was discussed in our previous article- Peripheral blood leukocyte culture. You can read it there. Here I am discussing only the overview of the entire process.
What is a karyotype?
Karyotyping is a technique to grow chromosomes, while karyotype is a method or procedure to arrange it using either manual method or computational software.
Applications of karyotyping
Though karyotyping is a traditional method, it is more effective and accurate to encounter ploidy and major deletions.
Recent advancements
A karyotype test is one kind of genetic testing method employed to detect various chromosomal anomalies. As we said, it is a cell culture method in which blood, bone marrow, biopsy, and other tissues can be cultured.
Conclusion
The karyotyping test is so traditional but recent automation made it more robust and accurate to detect various anomalies. Nowadays, a powerful microscope and computer systems are available which are quick, robust, and extremely accurate.
History
A Swiss botanist, Carl Wilhelm von Nageli was the first person who observed chromosomes in 1842. What he observed was a thread-like structure and he named it as transitory cytoplasts.
Definition
Karyotyping is a cytogenetic technique using which a karyogram or chromosomes are arranged in order to encounter various chromosomal abnormalities.
Principle of Karyotyping
The karyotyping is a combination of various other technique in which the cell culture technique is so crucial to use correctly.
Procedure
Any bodily fluid having dividing cells can be cultured, however, blood, amniotic fluid, solid tissue, tumor, chorionic villi are common samples used in karyotyping.
Protocol
The protocol for PBLC (Peripheral Blood Leukocyte Culture) is explained in the article here: Karyotyping protocol from Blood.
Staining and Banding techniques
Giemsa staining and GTG banding are techniques commonly used in karyotyping. The process of Giemsa staining is explained here.
Advantages
The cytogenetic techniques, especially, the karyotyping method is utilized to observe chromosomes. In a PCR, we can’t amplify the entire genome or whole chromosome DNA.
