'''
An organism with a very small genome has 3 chromosome pairs of 6, 8, and 10 
bases. You get a list of these chromosomes in order (i.e., the first two 
entries are your chromosome 1 set, the second two entries are the chromosome 
2 set, etc.). 

You want to mutate chromosome 3 such that the 7th base becomes a "G" in both 
copies. Use square brackets to access chromosomes and nucleotide bases.
'''

genome = ["CGTACG", "GTCTAT", 
          "ATTCTACA", "TGCAAGCT",
          "TGCGCACTAC", "ATGCTATCTG"]

# Start your solution here