Which of the following procedures is used as a routine technique for karyotyping using light microscopy?
**Core Concept**
Chromosomal analysis, specifically karyotyping, involves the examination of an individual's chromosomes to identify any genetic abnormalities. Routine karyotyping using light microscopy relies on the preparation of chromosomes in a specific state, allowing for accurate identification and analysis.
**Why the Correct Answer is Right**
G-banding is a widely used technique for karyotyping, where chromosomes are treated with trypsin and stained with Giemsa. This process creates distinctive banding patterns on the chromosomes, allowing for the identification of specific chromosomes and the detection of any genetic abnormalities. The G-banding technique is particularly useful for identifying translocations, deletions, and duplications. The banding patterns are the result of the differential digestion of the chromatin by trypsin, which creates regions of varying density that can be stained differently.
**Why Each Wrong Option is Incorrect**
**Option A:** Chromosomal microarray analysis is a molecular cytogenetic technique that uses high-density microarrays to detect copy number variations (CNVs) and other types of genetic alterations. While it is a powerful tool for identifying genetic abnormalities, it is not a routine technique for karyotyping using light microscopy.
**Option B:** Fluorescence in situ hybridization (FISH) is a molecular cytogenetic technique that uses fluorescently labeled probes to detect specific DNA sequences on chromosomes. While FISH is useful for identifying specific genetic abnormalities, it is not a routine technique for karyotyping using light microscopy.
**Option C:** Spectral karyotyping (SKY) is a technique that uses multiple fluorescent dyes to stain chromosomes, allowing for the identification of specific chromosomes and the detection of genetic abnormalities. While SKY is a powerful tool for karyotyping, it requires specialized equipment and is not a routine technique for karyotyping using light microscopy.
**Clinical Pearl / High-Yield Fact**
G-banding is a crucial technique in clinical genetics, as it allows for the accurate identification of genetic abnormalities that can be associated with various diseases, such as Down syndrome, Turner syndrome, and certain types of leukemia.
**Correct Answer: C. Spectral karyotyping (SKY) is a technique that uses multiple fluorescent dyes to stain chromosomes, allowing for the identification of specific chromosomes and the detection of genetic abnormalities. While SKY is a powerful tool for karyotyping, it requires specialized equipment and is not a routine technique for karyotyping using light microscopy.