Question

can someone explain what 7-deaza-dGTP is and why it is useful for sequencing GC rich fragments?

Answer 1

7-deaza-dGTP (7-deaza-2-deoxyguanosine-5-triphosphate) is a modified dGTP using in special sequencing reactions in which the DNA needs to sequence usually G C rich. DNA sequencing method now in use is based on Sanger dideoxy sequencing. the method involves on PCR reaction in which deoxynucleotides are using for chain terminaiton and further sequencer reading. In DNA G-C bond needs high melting temperature than A-T so if G/C content is higher in DNA it require more, sometimes this form secondary structures which limits strand separation for the sequencing reaction.7-deaza-dGTP is a modified dGTP analog which lacks a nitrogen at the seven position of the purine ring. The absence of this nitrogen destabilizes G-quadruplex formation by preventing Hoogsteen base pairing without affecting Watson-Crick base pairing. This reduces the strength of GC-rich duplexes by lowering the melting temperature. so we will get the sequence without much artifacts. I think you got it right

Answer 2

ahh, thank you! that makes sense.

Answer 3

Hello, Starwardd, can you please explain me about the G-quadruplex?

Answer 4

@rintu.kutum, that is one structure forming in high G rich regions in DNA. Sometimes it become difficult to separate at normal denaturing condition. One simplified with picture is available here please check
http://en.wikipedia.org/wiki/G-quadruplex