Summary
An organised picture of an individual's chromosomes arranged by size, used to detect abnormalities.
In depth
Cells are arrested in metaphase, stained and photographed; chromosomes are paired by size, banding pattern and centromere position. Karyotypes can detect aneuploidies (such as trisomy 21), translocations and large deletions.
Samples come from amniocentesis, chorionic villus sampling or blood.
Banding with Giemsa stain gives each chromosome a unique pattern of dark and light bands, and cytogeneticists describe locations such as 7q31 (long arm of chromosome 7, region 3, band 1). Fluorescence in situ hybridisation (FISH) paints specific sequences, and chromosome microarrays detect small deletions that a karyotype cannot see.
Samples come from blood lymphocytes, amniotic fluid cells (amniocentesis at about 15 to 20 weeks) or chorionic villi (10 to 13 weeks). Karyotypes are used to diagnose Down, Turner and Klinefelter syndromes, and the Philadelphia chromosome in leukaemia.
Remember: a karyotype shows the number and large-scale structure of chromosomes, not single gene mutations.
Frequently asked questions
What is Karyotype?
An organised picture of an individual's chromosomes arranged by size, used to detect abnormalities.
Which area of biology covers Karyotype, and how advanced is it?
Karyotype is one of the 54 topics in Genetics. It is rated Beginner, so it suits learners who are starting out in biology. Related topics in this area include Chromosomal Mutations, Chromosomes, Turner and Klinefelter Syndromes.
Can you give an example of Karyotype?
A Turner syndrome karyotype shows 45,X.
What should I learn before Karyotype?
Karyotype is a Beginner topic, so no earlier topic is required. Other Beginner topics in Genetics that pair well with it include Heredity, Gene, Allele.
What topics are related to Karyotype?
The closest topics to Karyotype are Chromosomal Mutations, Chromosomes, Turner and Klinefelter Syndromes, Nondisjunction. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Karyotype?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Karyotype. To practise the whole of Genetics, use the Genetics quiz.
How is Karyotype different from Chromosomal Mutations?
Karyotype: An organised picture of an individual's chromosomes arranged by size, used to detect abnormalities. Chromosomal Mutations: Large structural changes including deletions, duplications, inversions and translocations of chromosome segments. Read both side by side and note what each one explains.
How should I study Karyotype step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Chromosomal Mutations and explain the difference aloud. Finally, take the Genetics quiz and come back to this page for any question you miss.