Karyotype testing: a comprehensive guide to abnormality diagnosis

Karyotype test is an advanced **cytogenetic** method to check the **number, structure and shape of chromosomes** in human cells. This test can detect genetic abnormalities such as "Down syndrome, Turner or Klinefelter" and is used in cases such as "infertility, recurrent miscarriage or certain cancers"

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**1. What is karyotype?** - **Definition:** A karyotype is a picture of an individual's chromosomes arranged according to **size, shape and banding pattern** - **Number of normal chromosomes:** A healthy human has **46 chromosomes** (23 pairs), two of which are sex chromosomes (**XX in women and XY in men**). - **The purpose of the test:** to identify **numerical changes** (such as trisomy 21) or **structural** (such as chromosomal translocation or deletion) **2. Test method ** ### **A) Sampling** **Peripheral blood** (the most common method) - **amniotic fluid** (in pregnancy, from the 15th week onwards) - **placental villi (CVS)** (between 10-13 weeks of pregnancy) - **bone marrow** (to detect blood cancers such as leukemia) ### **b) Testing procedures in the laboratory** 1. **Cell culture:** Cells are grown in a special culture medium 2. **stopping cell division:** at the stage of **metaphase** (when the chromosomes are visible) 3. **Painting:** with techniques such as **G-banding** to create a banding pattern 4. **Microscope and analysis:** Chromosomes are examined and photographed under the microscope **Response time:** about **2-3 weeks** **3. Applications of karyotype testing** ### **a) diagnosis of genetic diseases** - Down syndrome (trisomy 21) - **Turner syndrome** (45,X) 4. - **Klinefelter syndrome** (47,XXY)

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Is it possible to prevent genetic diseases with pregnancy genetic testing? - Chromosomal disorders such as **balanced translocation** in parents ### **c) diagnosis of cancers** - Identification of **Philadelphia chromosome** in chronic myeloid leukemia (CML) ### **d) prenatal screening** - For pregnant women over **35 years old** or with a family history of chromosomal abnormalities **4. Interpretation of results** - **Natural result:** - Men: **46,XY** - Women: **46,XX**. - **Abnormal result:** - **Numerical changes:** such as **47,XX+21** (Down syndrome). - **Structural changes:** such as displacement between chromosomes 9 and 22 in leukemia **5. Who should test?** Couples with a history of infertility or frequent miscarriage ✅ Babies with **congenital abnormalities or growth delay** ✅ People with **family history of genetic diseases** ✅ Patients with **blood cancers** (such as leukemia) **6. Test limitations** - **failure to detect small gene mutations** (requirement of molecular tests such as NGS). - **Time-consuming** (compared to newer methods such as NIPT) ### **Conclusion** Karyotype testing is a **fundamental tool in medical genetics** used to diagnose chromosomal abnormalities. If you are in the high-risk group, consult a geneticist. > Kausar Pathobiology Specialized Laboratory, proud to obtain ISO 15189, ISO 10002 and ISO 9001 of the European Union, under the supervision of Dr. Ali Ayatollahi, an anatomical and clinical pathology specialist, covers more than a thousand cases of various tests in the fields of pathology, genetics and clinical. (Contract party of basic insurances and most supplementary insurances) Also, genetic counseling is provided free of charge in this center by experts.* > > *Address: Mashhad - Vakilabad - Kausar Blvd. - between 2 and 4 Kausar - Farabi Doctors Building - negative one floor. Contact numbers: 051-38840404 and 051-38820202 and 09028840404* > > **Kowsar specialized laboratory, having the equipment and experienced personnel, is able to perform sampling services at home in Mashhad.**