Which method is used for genetic testing that involves direct sequencing of DNA?

• A. In situ hybridization
• B. Karyotyping
• C. Amniocentesis
• D. DNA sequencing

Answer: (D)

DNA sequencing is a method specifically designed to determine the precise order of nucleotides within a DNA molecule. This technique allows for the identification of genetic variations or mutations by directly analyzing the DNA sequence. It involves breaking the DNA into smaller fragments, amplifying them, and then using various chemical reactions to read the sequence of bases (adenine, thymine, cytosine, and guanine) in the DNA.

In the context of genetic testing, this method is invaluable as it provides detailed insights into genetic disorders, allowing for precise diagnosis and the understanding of hereditary conditions. The ability to sequence DNA directly means that any changes or anomalies in the genetic code can be detected, facilitating targeted therapies and more informed health decisions.

The other methods mentioned serve different purposes and are not primarily focused on direct DNA sequencing. For instance, in situ hybridization typically aids in locating specific DNA sequences within the context of a whole cell or tissue section using labeled probes. Karyotyping is a technique that provides a visual representation of an individual's chromosomes, showing their number and structure but does not sequence the DNA itself. Amniocentesis is a procedure used to collect amniotic fluid to test for genetic disorders but does not involve the sequencing of DNA unless combined with subsequent techniques