What is the primary function of microarrays in biotechnology?

The primary function of microarrays in biotechnology is to measure the expression levels of many genes simultaneously. Microarrays are powerful tools that allow researchers to monitor gene expression patterns across thousands of genes at once. By using complementary DNA or RNA samples that are labeled and applied to a microarray, scientists can identify which genes are active in a particular cell type, tissue, or condition. This ability to analyze multiple genes in parallel provides valuable insights into the functional genomics of organisms, helping to understand complex biological processes, disease mechanisms, and responses to treatments.

This capability is distinct from the other options listed. For instance, techniques to visually observe cells under a microscope are not directly related to measuring gene expression but rather focus on cellular structures and morphology. Similarly, the separation of proteins based on size is typically achieved using gel electrophoresis, a different method entirely that does not involve the simultaneous measurement of gene expression. Lastly, analyzing the structure of DNA might involve techniques such as sequencing or PCR, rather than microarrays, which are specifically designed for expression profiling rather than structural analysis.