Final answer:
True, a DNA microarray contains labeled oligonucleotides that are tagged with fluorescent dyes, which are essential for visualizing hybridization patterns to determine gene expression levels or sequence differences.
Step-by-step explanation:
True, a DNA microarray contains oligonucleotides that are indeed labeled, typically with different fluorescent dyes. These labels are critical for the operation of the microarray because they allow researchers to visualize the hybridization patterns and thus determine the gene expression levels or identify differences in gene sequences between samples. During the microarray process, genomic DNA or cDNA derived from mRNA is labeled with fluorescent dyes (e.g., red or green), and after being combined in equal amounts, they are added to the microarray chip. The hybridization can then be monitored by measuring the intensity of fluorescence at specific spots on the chip to determine the binding of sample nucleic acids.
For instance, if genomic DNA or cDNA from two different samples is labeled with red and green fluorescent dyes, respectively, and hybridizes to the same spot on the microarray, that spot will appear yellow due to the combination of red and green. This indicates that nucleic acids from both samples have hybridized to that spot.
The use of fluorescently tagged molecules makes it possible to carry out transcriptional profiling, genotyping, or the investigation of single nucleotide polymorphisms (SNPs) by detecting and quantifying the hybridized fragments visually. Thus, the presence of a label on the oligonucleotides is essential for the function of DNA microarrays.