Used to determine the number and structure of chromosomes
Karyotype analysis
May be used to diagnose a chromosomal trisomy, sex chromosome disorders, translocations, and larger deletions or duplications
Microarray
Currently the preferred first line test used to diagnose microdeletion/microduplication syndromes, such as 22q11.2 deletion syndrome
Fluorescence in situ hybridization (FISH)
A targeted test that may be also used to look for the presence of a specific sequence of DNA on a chromosome
Methylation studies
Performed to help diagnose specific imprinting disorders (e.g., Prader–Willi syndrome)
Methylation
When methyl groups are added to DNA, the activities of the DNA segment can change
This physiologic process plays a role in X chromosome inactivation and imprinting, but also plays a role in pathologic processes such as aging, carcinogenesis, and the development of imprinting disorders such as Prader–Willi
Gene sequencing
Performed to look for mutations in a specific gene (e.g., fibrillin1 sequencing to diagnose Marfan syndrome)
Exome sequencing
Looks for potential disease-causing mutations in the protein coding regions (exons) of nearly the entire genome
Useful when there is a broad differential diagnosis of genetic conditions
