Which testing approach can detect both large and small deletions and duplications?

The correct answer is microarray, as it is a high-resolution genomic technology capable of detecting both large and small deletions and duplications across the genome. Microarray analysis assesses the copy number variations (CNVs) by comparing the test sample DNA to a reference genome, allowing for the identification of submicroscopic alterations that traditional methods might miss. This provides a comprehensive overview of genomic changes, which is particularly valuable in genetic counseling and diagnosis of genetic disorders.

Karyotype analysis, although useful for identifying large chromosomal abnormalities, typically cannot detect smaller deletions or duplications because it examines the structure and number of chromosomes at a lower resolution.

FISH (Fluorescence In Situ Hybridization) is a more targeted approach that can identify specific chromosomal abnormalities and is effective for detecting known large deletions or duplications but is limited in scope and cannot assess the entire genome for smaller abnormalities.

Southern blotting is primarily used for detecting specific DNA sequences and can identify large deletions or duplications, but it is less efficient for high-throughput analysis and does not provide comprehensive data on widespread genomic alterations.

In summary, microarray technology stands out for its ability to detect a wide range of genomic changes, making it the most suitable approach for