Types of Genetic Tests

• Karyotype analysis


  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