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Biology-Related Homework Help Cell Biology Topic started by: Valentine10 on Nov 4, 2010



Title: Palindromic DNA sequence
Post by: Valentine10 on Nov 4, 2010
I just can't seem to get this question right at all!

'The restriction endonuclease Sac I recognises a 6-nucleotide palindromic DNA sequence whose first three bases are 5 prime - GAG - 3 prime. Sac I cuts to give a 4 - nucleotide 3 prime overhang that is centred on the middle of the sequence. What is the base sequence of the 4 - nucleotide overhang when read towards the free end of the chain?

3 Prime - TGCA - 5 Prime
3 Prime - AGGA - 5 Prime
5 Prime - AGGA - 3 Prime
5 Prime - TCGA - 3 Prime
5 Prime - AGCT - 3 Prime

Any help would be greatly appreciated! :)


Title: Re: Palindromic DNA sequence
Post by: bio_man on Nov 4, 2010
Here's an example of a palindromic sequence:

5'- G  A  A  T  T  C -3'
3'- C  T  T  A  A  G -5'

I think it's:

3 Prime - TGCA - 5 Prime ... because
3 Prime - ACGT - 5 Prime

And I chose this instead of 5 Prime - AGCT - 3 Prime because the question states 5 to 3 and the opposite of this would be 3 to 5.


Title: Re: Palindromic DNA sequence
Post by: Valentine10 on Nov 5, 2010
Thank you! :)