A palindrome in DNA has the same base order on the two strands when both are read from 5 prime to 3…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A palindrome in DNA has the same base order on the two strands when both are read from 5 prime to 3 prime. Eight short sequences are given, each read from 5 prime to 3 prime on the top strand.
GAATTC, GGTACC, GACGTC, GATTAC, CCCGGG, TTAGCA, AAGCTT, CGCGCA
How many of the eight are palindromic sequences? Say how you tested them.
Need a reminder? The key ideaShow
A restriction endonuclease cuts both strands inside its palindromic recognition sequence. A site of bases turns up by chance about once in bases. A straight DNA with sites gives fragments. A circular DNA with sites gives fragments.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Given. Eight sequences.
Plan. For each sequence, pair the bases and then reverse the result. If it equals the original, the sequence is a palindrome.
Step 1. GAATTC pairs to CTTAAG. Reversed, GAATTC. Same: yes.
Step 2. GGTACC gives CCATGG, reversed GGTACC: yes. GACGTC gives CTGCAG, reversed GACGTC: yes.
Step 3. GATTAC gives CTAATG, reversed GTAATC: different, no.
Step 4. CCCGGG gives GGGCCC, reversed CCCGGG: yes. TTAGCA gives AATCGT, reversed TGCTAA: no.
Step 5. AAGCTT gives TTCGAA, reversed AAGCTT: yes. CGCGCA gives GCGCGT, reversed TGCGCG: no.
Answer: sequences are palindromic.
Check. The palindromes are GAATTC, GGTACC, GACGTC, CCCGGG and AAGCTT.
Watch out. A sequence that reads the same backwards on one strand, such as GATTAG, is not necessarily a palindrome in DNA.
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