Karyotype Practice Online: Sample Cases with Answers

Last updated: October 22, 2026

The fastest way to get good at karyotyping is to analyze a lot of metaphases and check every answer. Start with these worked sample cases, each explained with its ISCN result and what to look for, then practice on real metaphase spreads.

Sample cases

Each case gives the ISCN result, what each part of the notation means, what to look for when you karyotype the cell, and the related karyotypes you will meet in practice.

47,XX,+21Trisomy 21 (Down syndrome)Three copies of chromosome 21. The most common autosomal trisomy in live births. 47,XY,+18Trisomy 18 (Edwards syndrome)Three copies of chromosome 18. Telling 18 from 17 is the key skill. 47,XX,+13Trisomy 13 (Patau syndrome)Three copies of chromosome 13. Sorting the D-group acrocentrics is the key skill. 45,X45,X (Turner syndrome)A single X chromosome. Counting carefully and looking for mosaicism are the key skills. 47,XXY47,XXY (Klinefelter syndrome)An extra X chromosome in a male. Telling the X from chromosome 7 is the key skill. 46,XY,t(9;22)(q34;q11.2)[20]Philadelphia chromosome, t(9;22)The hallmark translocation of chronic myeloid leukemia, in a bone marrow karyotype.

How to practice so that you improve

Practice works best when it copies what happens at the bench: you see a metaphase, you analyze it, and you commit to a result before anyone tells you the answer.

  1. Count first. Count every chromosome before you start sorting. A count of 45 or 47 tells you what to look for.
  2. Sort by group, then by band. Use size and centromere position to place each chromosome in its group, then the landmark bands to identify it.
  3. Compare homologs band by band. Most structural changes show up as a difference between the two copies of a chromosome.
  4. Write the ISCN before you check. Then compare your answer with the key and note every difference. The ISCN examples page shows the correct form for the common results.
  5. Keep an error log. Record which chromosomes you misplaced and which abnormalities you missed, and work on those first.

What a good practice set includes

  • Normal karyotypes, so that chromosome identification becomes automatic and you know what normal variation looks like.
  • Numerical abnormalities, including sex chromosome changes and mosaic cases.
  • Structural abnormalities: balanced and unbalanced translocations, deletions, duplications, inversions, isochromosomes and rings.
  • Prenatal cases, which are often analyzed at a lower band level.
  • Cancer karyotypes, with clones, recurrent translocations and poorer chromosome morphology.

Practicing online with Karyotutor

Karyotutor is built for exactly this kind of practice. You work on real G-banded metaphase spreads in your browser: drag each chromosome into the karyogram, rotate it into position, and score your work as soon as you finish. The case library has more than 120 cases covering constitutional, prenatal and cancer karyotypes, and reference ideograms are there when you need them.

Educators and laboratory training programs can assign cases to trainees, set block tests and review every trainee's results. See Karyotutor for educators.

Keep learning

How to karyotypeThe full workflow from metaphase to ISCN result, with the mistakes trainees make most often. G-banding patterns, chromosomes 1 to 22, X and YLandmark bands for every chromosome, and how to tell apart the pairs that look alike. ISCN notation examplesHow to read and write karyotypes, with worked numerical, structural, mosaic and cancer examples.

Browse the full Learning Hub

This page is for education and training. It is not medical advice and must not be used to diagnose or treat anyone. Laboratory results should be interpreted by qualified professionals following current standards.