Consider the two DNA sequences ACCG and CG. We want to align
them with the Needleman-Wunsch algorithm. First we need to
compute the optimal scoring matrix V shown below. The empty
string is denoted by O.

  O  A  C  C  G
O 0  
C
G

Let the match cost be 5, mismatch -4, and gap -20. 

a. Write out the first row and column of V (2 pts)

b. Write out second row of V using the Needleman-Wunsch 
recurrence (5 pts)

                                V[i-1,j-1] + m (or mm)
                V[i,j] = max{   V[i-1,j]+g
                                V[i,j-1]+g

c. Write out the traceback matrix as well. (2 pts)

d. Finally write the final alignment given by your traceback
matrix. (1 pt)
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Write a Python function that returns the Needleman-Wunsch score
between two DNA sequences seq1 and seq2 (5 pts). 
Your function definition would be

def NWscore(seq1, seq2, m, mm, g):

where seq1 and seq2 are DNA sequences, and m, mm, and g are
match, mismatch, and gap costs. 

Submit hardcopies in class on Feb 9th.