Final answer:
BLAST is used to identify related sequences to a given DNA sequence in the GenBank database, and it is not used for determining restriction sites, identifying promoter sequences, or splice sites.
Step-by-step explanation:
The program BLAST (Basic Local Alignment Search Tool) is a bioinformatics tool used for comparing an input nucleotide or protein sequence with a database of sequences to identify database sequences that resemble the query sequence above a certain threshold. Specifically, BLAST is best used to identify related sequences to a given DNA sequence in the GenBank database.
While BLAST can be used in a number of genomic analyses, it is not involved in tasks like determining what restriction sites are present in a DNA fragment, identifying promoter sequences, or pinpointing splice donor and acceptor sites. These tasks are performed using different molecular techniques, including restriction enzyme mapping, promoter analysis, and RNA splicing studies.