Counting Our genetic material, DNA, is formed from a 4 letter \"alphabet\" of ba
ID: 3047215 • Letter: C
Question
Counting Our genetic material, DNA, is formed from a 4 letter "alphabet" of bases: A, T, G, C (adenine, thymine, guanine, and cytosine). The order in which the letters are arranged is important, but because a molecule can move, there is no difference between a sequence and the same sequence reversed. For example, the sequence (A, A, T, A, G, A, T) is the same as the sequence (T A, G, A, T, A, A). (In reality, DNA molecules have identifiable ends, but ignore that in this problem.) Problem 6 How many distinct DNA sequences of 12 bases are there? (Q6)Explanation / Answer
I think the only reversed sequences you need to worry about arepalindromes since for DNA, the combinations of nucleotides are likewords and the reverse of a word is distinct from the original word;that is the word "apple" is not the same as it's reverse"elppa".
Anyways, first calculate the number of combinations of bases youcan get, that's 4^6. Since palindromes don't count you cansubtract the number of palindromes from 4^6. The number ofpalindromes is just the number of distinct sequences of 3 baseswhich is 4^3. So I guess the # of distinct non palindromicsequences is 4^6-4^3 which is 4032. I suppose if youignore the directionality of DNA then the reverse sequence is thesame as the original sequence in which case you need to divide 4032by 2. You then add the number of palindromes, 4^3 or 64 to thatnumber to get 2080 distinct 6 nucleotide sequences.