Question

Which of the following methods is/are used for local alignment of nucleotide sequences?

• A. Smith-Waterman algorithm
• B. Needleman-Wunsch algorithm
• C. BLAST
• D. Neighbour-joining method

Hint:

Smith-Waterman and BLAST are used for local alignment, whereas Needleman-Wunsch is used for global alignment and Neighbour-joining is used for phylogenetic analysis.

Answer 1

The Correct Option is A, C

Step 1: Understand sequence alignment.
Sequence alignment is a computational method used to compare nucleotide or protein sequences in order to identify regions of similarity, evolutionary relationships, or functional conservation.

Step 2: Understand local alignment.
Local alignment identifies highly similar regions within two sequences instead of aligning the entire sequence length. It is useful when sequences share only partial similarity.

Step 3: Analyze Smith-Waterman algorithm.
The Smith-Waterman algorithm is specifically designed for local sequence alignment using dynamic programming. It identifies the best matching local regions between sequences.
Hence, option (A) is correct.

Step 4: Analyze Needleman-Wunsch algorithm.
Needleman-Wunsch algorithm performs global alignment, where the complete lengths of two sequences are aligned from beginning to end.
Therefore, option (B) is incorrect for local alignment.

Step 5: Analyze BLAST.
BLAST (Basic Local Alignment Search Tool) is widely used for rapid local alignment searches against sequence databases. It identifies regions of local similarity between sequences.
Hence, option (C) is correct.

Step 6: Analyze Neighbour-joining method.
Neighbour-joining is a phylogenetic tree construction method and is not an alignment algorithm.
Therefore, option (D) is incorrect.

Step 7: Final conclusion.
Thus, the methods used for local alignment of nucleotide sequences are
\[ \boxed{(A)\text{ and }(C)} \]