Question

How is BLAST used to analyse sequence similarity ? Explain.

Hint:

Remember BLAST and other computational tools are useful in bioinformatics for analyzing sequence data.

Answer 1

(i) BLAST for Analyzing Sequence Similarity: Basic Local Alignment Search Tool (BLAST) is a bioinformatics tool used to find regions of local similarity between sequences. BLAST works by comparing a given DNA or protein sequence with sequences in databases using matrices that give scores for the alignment of these sequences. Matches receive a reward score, and mismatches receive a penalty, and these scores are added to arrive at a final score for the alignment. Top-scoring matches are ranked based on whether the match was due to an ancestral relationship or just by random chance, and matches with high similarity can be useful in identifying genes or proteins of interest. True matches are then examined using ENTREZ. (ii) Computer Programs for Gene Prediction: GeneMark is a program that can perform gene prediction for bacterial genomes. GENSCAN is a program that is used to predict the presence of genes in eukaryotic genomes.