AT content of a DNA Sequence
y = btd_atcontent(x)
input DNA sequence (string)
holds output AT content (percentage, as a string)
y = btd_atcontent(b)
calulates the number of A and T in a given
DNA sequence b.
--> y = btd_atcontent("ATCGATCGATCGTATATGCTAGCTA") y = 60 %