A karyotype is an individual's collection of chromosomes. The term also refers to a laboratory technique that produces an image of an individual's chromosomes. The karyotype is used to look for abnormal numbers or structures of chromosomes.
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When I hear the word "karyotype", I think about a picture of chromosomes. When somebody has their blood studied to look at how many chromosomes they have and whether the chromosomes are complete, we come up with a picture in which we can line up all the chromosomes and count them. That way we can tell whether or not somebody has all the proper number of chromosomes, which is 46, and that way we can look at the X and the Y chromosomes and determine if it's a female or male. Somebody might order a chromosome study and look at a karyotype if they were worried that a child might have an extra or missing bit of chromosome material. So one of the most common things we can see on karyotyping is an extra Chromosome 21, which is associated with Down syndrome. We also get karyotypes when pregnant women choose to have testing on their unborn fetus, and the karyotype allows the providers to look at and count the chromosomes to determine whether or not the child is affected by having an extra chromosome.
Barbara Bowles Biesecker, Ph.D.
Associate Investigator, Social and Behavioral Research Branch; Head, Genetic Services Research Unit; Director, JHU/NHGRI Genetic Counseling Training Program
Ms. Biesecker's research and teaching activities focus on making genetic counseling as effective as possible, which is a growing challenge as new genetic technologies generate an avalanche of data and questions about the meaning of genetic tests. This data has highlighted the fact that behavioral researchers do not yet know enough about the best ways to help people decide how to use their own genetic information in making health and reproductive decisions. Since genetic counseling has a relatively sparse amount of research to guide its professionals, Ms. Biesecker and her colleagues are on the cutting edge of genetic counseling research.