# Isolating Symbols in Alignments solved by 113

Feb. 15, 2013, 10:37 p.m. by Rosalind Team

Topics: Alignment, Dynamic Programming

## How Much Does it Cost to Align Two Symbols?

As we saw in “Counting Optimal Alignments”, there will usually be a huge number of different optimal alignments of two given strings. In this problem, which represents a first attempt to understand how much optimal alignments can differ, we will select two symbols at a time from the two strings and ask how much the maximum alignment score can differ from the optimal score if we demand that these two symbols must be aligned (i.e., implying that one symbol must be substituted for the other).

## Problem

Say that we have two strings $s$ and $t$ of respective lengths $m$ and $n$ and an alignment score. Let's define a matrix $\mathrm{M}$ corresponding to $s$ and $t$ by setting $\mathrm{M}_{j, k}$ equal to the maximum score of any alignment that aligns $s[j]$ with $t[k]$. So each entry in $\mathrm{M}$ can be equal to at most the maximum score of any alignment of $s$ and $t$.

Given: Two DNA strings $s$ and $t$ in FASTA format, each having length at most 1000 bp.

Return: The maximum alignment score of a global alignment of $s$ and $t$, followed by the sum of all elements of the matrix $\mathrm{M}$ corresponding to $s$ and $t$ that was defined above. Apply the mismatch score introduced in “Finding a Motif with Modifications”.

## Sample Dataset

>Rosalind_35
ATAGATA
>Rosalind_5
ACAGGTA


## Sample Output

3
-139


## Citation

This problem follows Jones & Pevzner, An Introduction to Bioinformatics Algorithms, Problem 6.21

## Hint

For the sample dataset $\mathrm{M} = \begin{bmatrix} 3 & 0 &-1 &-4 &-5 &-10 &-11\\ 0 & 3 & 0 &-1 &-4 & -7 &-10\\ -1 & 0 & 3 &-2 &-1 & -6 & -7\\ -4 & -1 & 0 & 3 & 0 & -3 & -6\\ -7 & -4 &-3 & 2 & 3 & 0 & -3\\ -10 & -5 &-6 &-3 & 0 & 3 & -2\\ -11 &-10 &-5 &-6 &-1 & -2 & 3 \end{bmatrix}$