What type of molecules are siRNA and miRNA considered?

siRNA (small interfering RNA) and miRNA (microRNA) are small RNA molecules that play critical roles in the regulation of gene expression. They are single-stranded RNA molecules typically 20-24 nucleotides in length. Both siRNA and miRNA are derived from longer precursor RNA molecules and are involved in the RNA interference (RNAi) pathway, where they can bind to complementary mRNA sequences and either promote degradation of the mRNA or inhibit its translation into protein. This ability to bind to specific mRNA sequences allows siRNA and miRNA to act as regulatory components in various biological processes, including development, defense against viruses, and cellular response to stress.

Thus, referring to siRNA and miRNA as nucleotide sequences accurately describes their structural composition as they are made up of nucleotides, the building blocks of RNA.