Microarrays quantify signals from transcripts represented on a predefined set of probes, whereas RNA sequencing reads complementary DNA-derived sequences and can reveal transcripts outside that set. This makes sequencing useful when researchers want to detect previously unrecognized transcripts or splice variants, while microarrays support expression comparisons using an established transcript collection.
Complementary DNA provides a molecular form of the original RNA that can be measured by the selected profiling platform. After RNA isolation, conversion to complementary DNA precedes quantification with approaches such as microarrays or RNA sequencing. The resulting measurements reflect transcript abundance, allowing expression levels to be compared among biological samples.
RNA sequencing can identify previously unrecognized transcripts and splice variants in addition to measuring expression patterns. This broader sequence-based view helps researchers examine which RNA forms are present, not only whether a familiar transcript changes in abundance. Consequently, sequencing can expand the set of transcripts considered in studies of gene regulation and cellular state.
Differences in profiles indicate that transcript levels vary between the samples, but their biological meaning depends on the comparison being made. Profiles can distinguish cell types, developmental states, disease-associated changes, or responses to environmental conditions and treatments. Researchers can then use these patterns to investigate gene regulation and identify altered biological pathways.
A basic workflow begins by isolating RNA from the biological samples being compared. Depending on the chosen approach, the RNA is converted to complementary DNA, followed by transcript quantification with a microarray or RNA sequencing method. Researchers then compare the resulting expression profiles across samples to identify differences relevant to the biological question.
Researchers may choose this approach when they need to compare gene activity across distinct biological conditions. Suitable comparisons include different cell types, developmental states, disease-associated samples, or treated and untreated material. The resulting profiles can reveal coordinated expression changes and provide evidence for how cells respond to environmental conditions or experimental treatments.
Comparative profiles support several downstream biological investigations, including biomarker discovery, pathway analysis, and studies of gene regulation. They can also help characterize cellular identity and developmental state or describe changes associated with disease and treatment response. These applications use expression patterns as evidence for distinguishing biological conditions and identifying transcripts or processes associated with them.