Palindromic sequence Question! Please help!!

[neplina]

A single point mutation in a gene results in a nonfunctional protein. Individuals heterozygous for this mutation were identified using a Southern blot. Which pair of WT and mutant alleles most likely contains the mutation?

A) WT: 5-TAGTCGAAGCTTAGGCATCT-3
Mt: 5-TAGTCGATGCTTAGGCATCT-3

B) WT: 5-TAGTCGAAGCTTAGGCATCT-3
Mt: 5-TAGTTGAAGCTTAGGCATCT-3

Could someone please explain to me why the ans is A? Im having a hard time with palindromic sequences.

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[Matthew9Thirtyfive]

Palindromic sequences are sequences where the complementary strand, when read 5’-3’ is the same. In the WT strand above, the palindromic sequence is AAGCTT. You can see why this is palindromic when you put the complementary strand with it:

5’-AAGCTT-3’
3’-TTCGAA-5’

So when the complement is read 5’ to 3’, it is AAGCTT—the exact sequence.

Then, you just pick the answer with a mutation in the palindromic sequence. That’s A (it has a T instead of an A).

 

[neplina]

Perfect, thanks!