Comparing sequences is one of the oldest and most useful tasks in bioinformatics. When two sequences are similar, they often share a function or a common ancestor, so sequence alignment lets you transfer what is known about one gene or protein to another.
You'll start with the ideas behind alignment: how sequences are lined up, how substitutions are scored, and what homology means. You'll meet scoring matrices such as BLOSUM and the main tools, including ClustalW for multiple sequence alignment.
Then you'll put this into practice with BLAST, the Basic Local Alignment Search Tool from NCBI. You'll learn to set up a nucleotide or protein search, compare two or more sequences, and read the results. Once you've finished, move on to Sequencing Data & Quality Control.
A step-by-step guide to running a nucleotide or protein BLAST, reading the results, and creating an evolutionary tree from them.
How to use Nucleotide BLAST to align and compare two or more DNA sequences.
A tutorial on using BLAST presented by NCBI, the group that runs it.