ACGTG

ACGTG is a pentanucleotide sequence found in DNA, consisting of the nucleotides adenine (A), cytosine (C), guanine (G), thymine (T), and guanine (G). It is not a gene or a named molecule, but a specific five-letter string that can occur anywhere within a genome where DNA bases are present.

In statistical terms, the probability of finding ACGTG at a particular starting position in a completely random sequence with equal base frequencies is (1/4)^5, or about 0.0976%. Real genomes deviate from this simple model because of varying GC content and local sequence biases, so the actual frequency of ACGTG depends on the regional nucleotide composition. Regions with higher GC content will generally show a higher likelihood of sequences containing G and C, including ACGTG, than AT-rich regions.

Functional significance is context-dependent. The appearance of ACGTG by itself does not imply a universal regulatory function. It may be part of larger transcription factor binding motifs, splice sites, or other regulatory elements, but such roles are determined by the surrounding sequence and cellular context. Conversely, ACGTG can also appear in coding regions or in noncoding DNA without contributing to a known function.

Applications of the motif include teaching and practice in sequence analysis, motif searching, and enrichment calculations. As a simple example, ACGTG illustrates how short sequence motifs are treated in computational analyses and how their frequency can inform studies of genomic composition and motif occurrence.

See also: pentanucleotide, DNA sequence, motif discovery.