| KRATKA VSEBINA | V zadnjem obdobju smo priča znatnemu naraščanju uporabe mikroračunalnikov pri raziskavah in analizah zaporedij DNA. Molekule DNA so računalnikom najpogosteje predstavljene v obliki zapisov v formatu FASTA , ki kodirajo sekvence DNA v obliki ASCII niza štirih nukleotidnih oznak A, G, C in T, katerim se po potrebi pridružijo šedegenerativne kode in znak za presledek, ko gre za množice med seboj poravnanih zaporedij DNA. Zapis FASTA je dojemljiv za biologa in enostaven za programerja, ki razvija računalniški program, saj si pri razvoju lahko pomaga z bogatim naborom obstoječih knjinic za delo z znakovnimi polji. Kljub omenjenim prednostim ima zapis FASTA določene slabosti, kot je manj učinkovito iskanje zaporedij nukleotidov, še posebej ob prisotnosti degenerativnih kod. Druga slabost izvira iz dejstva, da vsak posamezni znakFASTA za presledek zasede po en zlog računalniškega pomnilnika,kar je ob prisotnosti velikega števila presledkov neučinkovito in tudi dodatno manjšahitrost iskanja nukleotidnih zaporedij. Zaradi omenjenih slabosti predstavljamo alternativni zapis zaporedij DNA, ki omogoča hitrejše iskanjenukleotidnih zaporedij in učinkovitejše shranjevanje informacij o poravnavi, kar vodi v hitrejše delovanje programov in odpira monost shranjevanja večjega števila zapisov DNA v delovni pomnilnik računalnika. // Microcomputers have become ubiquitous tools for DNA research and analysis. Before DNA sequences can be fed into computer programs they need to be suitably coded, which is usually done in a widely accepted FASTA format. According to this scheme, DNA sequence is represented as an ASCII string of four nucleotide characters A, G, C and T, possibly extended with additional codes for representation of degenerated sites, and a character code for FASTA blanks when dealing with aligned DNA sequences. FASTA representation is intuitive for biologists and it eases development of programs since developer scan utilize a myriad of available libraries for working with ASCII strings. Despite the mentioned advantages, FASTA format possesses certain drawbacks like inefficient searching for substrings, especially in the presence of degenerative codes. The second disadvantage is inefficient storage of FASTA blank characters, since each such characteroccupies one byte of memory. Substring searching speed is also negatively affected in the case of excessive number of blanks. Due to the stated drawbacks, we propose an alternative coding of DNA sequences, which enablesfaster searching of substrings and efficient storage of FASTA blanks, with the result that a greater set of DNA sequences can be held in working memory of a computer and processed faster. |