Final answer:
BLASTX uses six different reading frames to calculate possible protein sequences, including all three in both the forward and reverse directions.
Step-by-step explanation:
When performing a BLASTX analysis, the program uses six different reading frames to calculate the possible protein sequences.
This means that the DNA sequence is translated into amino acids in all possible reading frames: three in the forward direction (starting from the first, second, and third nucleotide) and three in the reverse complement of the sequence.
The logic being that a single nucleotide shift can change the entire amino acid sequence, so examining all six frames ensures that the correct protein coding region is identified.