Ruby 프로그램입니다.

'CGTAACAAGGTTTAGACCGTGGAATAA'.chars.each_slice(3).each {|x| puts x.join}

CGT
AAC
AAG
GTT
TAG
ACC
GTG
GAA
TAA

Python 3.6.3 (v3.6.3:2c5fed8, Oct  3 2017, 18:11:49) [MSC v.1900 64 bit (AMD64)] on win32 Type "copyright", "credits" or "license()" for more information.
>>> s = 'CGTAACAAGGTTTCCGTAGGTGAACCTGCGGAAGGATCATTGATGAGACCGTGGAATAAACGATCGAGTG AATCCGGAGGACCGGTGTACTCAGCTCACCGGGGGCATTGCTCCCGTGGTGACCCTGATTTGTTGTTGGG'
>>> tri = [ s[i:i+3] for i in range(0, len(s), 3) ]
>>> tri 
['CGT', 'AAC', 'AAG', 'GTT', 'TCC', 'GTA', 'GGT', 'GAA', 'CCT', 'GCG', 'GAA', 'GGA', 'TCA', 'TTG', 'ATG', 'AGA', 'CCG', 'TGG', 'AAT', 'AAA', 'CGA', 'TCG', 'AGT', 'G A', 'ATC', 'CGG', 'AGG', 'ACC', 'GGT', 'GTA', 'CTC', 'AGC', 'TCA', 'CCG', 'GGG', 'GCA', 'TTG', 'CTC', 'CCG', 'TGG', 'TGA', 'CCC', 'TGA', 'TTT', 'GTT', 'GTT', 'GGG']
>>> s == ''.join(tri) True
>>>