g

g

q

p

of this table vertically. Sequence y was placed on the top of this

izontally. Suppose previous alignments had done for three cells

, C), and (T, A). For the alignment of the cell (T, C), which was

econd residue T of sequence x and the second residue C of

y, there were three alignment (move) possibilities. They were the

om each of three aligned cells, i.e., the cells (C, A), (C, C) and (T,

iagonal move was from the cell (C, A) to the current cell (T, C).

uation, it was assumed that the first residue C of sequence x and

residue A of sequence y had been already aligned. The current

t therefore led to the alignment of CT versus AC. The horizontal

s from the left cell (T, A) to the current cell (T, C). In this situation,

umed that the previous alignment was the alignment of CT versus

cause the residue T of sequence x was used in the previous

t, the current residue C of sequence y had to be aligned with a

refore the current alignment led to the alignment of CTെ versus

e vertical move was from the top cell (C, C) to the current cell (T,

s situation, it was assumed that the previous alignment was the

t of Cെ versus AC and the current alignment resulted in CെT

Cെ. This is because the residue C of sequence y was used in the

alignment and a gap had to be inserted in sequence y to align with

ue T of sequence x.

The illustration of three incremental alignments used in the Sellers algorithm.

n three possible actions for continuing a homology alignment

remaining residues from two sequences, it is required to know