** Next:** Step 4
** Up:** Near Optimal Multiple Sequence
** Previous:** Step 2

Again, only those gaps of *a*_{k} are inserted into *t*_{k} and
*t*_{k+1} that are not already present in *t*_{k}.
Since each gap of sequence *a*_{k} that is considered is
inserted into *both*, *t*_{k} and *t*_{k+1}, the score of this
alignment is still optimal, as gap against gap scores zero. In
Figure 9 the down arrows correspond to this step.
The dark rectangles represent the inserted gaps.
After those two steps the partial score of the MSA and the
score between sequences *a*_{k} and *a*_{k+1} are both still
optimal.

*Chantal Korostensky*

*1999-07-14*