BLAST Tool and Sequence Alignment

The video tutorial by Bob Lesic from Johns Hopkins University covers the use of the BLAST tool, a bioinformatics resource for finding sequence similarities. It explains how to choose the right BLAST program, input sequences, select databases, run searches, and analyze results based on E-values. The tutorial also demonstrates how to interpret sequence alignments and provides guidance on editing and resubmitting searches.

What is the primary function of the BLAST tool in bioinformatics?

• To visualize protein structures

• To calculate molecular weights

• To search for related sequences in a database

• To edit DNA sequences

Which website is commonly used to access the BLAST tool?

• www.genome.gov

• www.ncbi.nlm.nih.gov

• www.protein.org

• www.dna.gov

If you start with a DNA sequence, which BLAST program should you use?

• Genome BLAST

• Protein BLAST

• Nucleotide BLAST

• Translated BLAST

What is the purpose of selecting a specific organism in the BLAST search?

• To enhance the accuracy of the sequence alignment

• To reduce the size of the input sequence

• To limit the search results to sequences from that organism

• To increase the search speed

What does a low E-value in BLAST results indicate?

• A low level of sequence similarity

• A high level of sequence similarity

• A need to rerun the search

• An error in the search process

In BLAST results, what does an E-value of 6e-21 signify?

• 6 divided by 21

• 6 times 10 to the power of -21

• 6 plus 21

• 6 times 10 to the power of 21

How many homologues to the rat protein were found in the human genome?

• 10

• 12

• 15

• 20

What percentage of amino acids were identical in the first alignment of the rat and human sequences?

• 55%

• 65%

• 75%

• 45%

What does a plus sign between amino acids in a BLAST alignment indicate?

• A mismatch

• An exact match

• A gap in the sequence

• A chemical similarity

What is the function of the 'edit and resubmit' button in BLAST?

• To delete the previous search

• To modify and rerun the previous search

• To start a new search from scratch

• To save the current search results