Final answer:
A BLASTX is conducted following a BLASTN to examine similarities at the protein level which may not be visible only by analyzing nucleotide sequences. This step is crucial to understand the function and evolutionary relationships of the genes.
Step-by-step explanation:
Performing a BLASTX after a BLASTN analysis on a DNA sequence is done to analyze sequence similarities at the protein level (b). BLASTN compares nucleotide sequences to sequence databases and locates sequences that resemble the query sequence with respect to their nucleotide order. BLASTX, however, translates the DNA sequence into all possible reading frames and compares these translated protein sequences against a protein sequence database. This can uncover potential functionalities encoded by the genomic sequence that may not be evident at the nucleotide level alone due to the degeneracy of the genetic code.
Furthermore, sequence alignments performed via tools like BLAST are instrumental in constructing evolutionary relationships or phylogenetic trees. They help in distinguishing homologous from analogous traits by revealing sequence conservation across different species. By using sequence alignments, we can understand the evolution of genes and gene families, and identify mutations or genetic disorders. This level of analysis is essential in bioinformatics, which includes applications like tracking genes through species to understand genetic disease and evolutionary relationships.