Cytogenetics

A branch of genetic testing that examines the number and structure of chromosomes using a special technique, this test is called karyotyping or chromosomal analysis. 

Karyotyping(chromosomal analysis):  is analysis of metaphase chromosomes using light microscope to take a photograph of the chromosomes. It can be run using blood sample, placenta or amniotic fluid and bone marrow cells. 

Indication for Karyotyping:

1. Infants, children and adults who have  symptoms that are suggestive of chromosomal abnormalities such as unexplained short stature, hypogonadism, dysmorphic features.
2. Infertility or Recurrent abortion. 
3. Diagnosis of Leukaemia.

Abnormalities that maybe detected:

1. Down syndrome (Trisomy 21)
2. Edward syndrome (Trisomy 18)
3. Patau syndrome (Trisomy 13)
4. Klinefelter's syndrome (XXY)
5. Turner syndrome (X)
6. Reciprocal and Robertsonian translocation which leads gain or loss of genetic material 

Chromosomal microarray analysis (CMA) is a molecular cytogenetic method for analyzing copy number variations. Enables detection of known and novel structural aberrations, such as copy number variations (CNVs), chromosomal imbalances, regions exhibiting loss/absence of heterozygosity (LOH), uniparental isodisomy (UPD), and mosaicism. 

Chromosomal microarray analysis is recommended as a first-step analysis for individuals with signs of intellectual disability, developmental delay, autism spectrum disorder, or multiple congenital anomalies, as it provides comprehensive genetic testing for the most common chromosomal conditions as well as a large number of severe genetic conditions not detected by traditional chromosome analysis. Additionally, it enables the detection of copy number variations and/or large deletions/duplications.