EtBr- It is a planar ,aromatic,intercatalytic agent. It is used in molecular biology labs as a fluroscent dye for nucleic acid gel electrophoresis.
It binds non covalently to ds Dna by intercatalyting into the stacked base pairs. It forms close vanderwall contacts with the base pairs of DNA and interact with hydrophobic interior of DNA molecule.
One EtBr molecule integrated upto 2.5 bp of DNA and causes the DNA to unwind by 27°C in covalently circular DNA .Hence, it decreses the number of helical turns. When EtBr binds to linear DNA it causes the helical pitch to increase.
Effects-
1.Ethidium Bromide (EtBr) is sometimes added to running buffer during the
separation of DNA fragments by agarose gel electrophoresis.The mobility of
DNA was always less in the gels with EtBr.
2.Ethidium bromide possesses UV absorbance maxima at 300 and 360 nm. It
can absorb energy from nucleotides excited by absorbance of 260 nm radiation.
Image source-http://sandwalk.blogspot.in/2007/07/ethidium-bromide-binds-to-dna.html
1.Ethidium Bromide is used in electrophoresis of DNA fragments because:
[a] It makes the fragments visible under UV light
[b] It makes the DNA fragments more mobile in the gel
[c] It increases the conductivity of electricity through the gel
[d] It helps determine the size of the fragments
Ans. A
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It binds non covalently to ds Dna by intercatalyting into the stacked base pairs. It forms close vanderwall contacts with the base pairs of DNA and interact with hydrophobic interior of DNA molecule.
One EtBr molecule integrated upto 2.5 bp of DNA and causes the DNA to unwind by 27°C in covalently circular DNA .Hence, it decreses the number of helical turns. When EtBr binds to linear DNA it causes the helical pitch to increase.
Effects-
1.Ethidium Bromide (EtBr) is sometimes added to running buffer during the
separation of DNA fragments by agarose gel electrophoresis.The mobility of
DNA was always less in the gels with EtBr.
2.Ethidium bromide possesses UV absorbance maxima at 300 and 360 nm. It
can absorb energy from nucleotides excited by absorbance of 260 nm radiation.
3.In covalently-closed circular DNA(plasmid), twist (turns)and writhe(supercoiling) are directly related. With ethidium, the negatively supercoiled plasmid ( E. coli) becomes positively supercoiled, and each additional ethidium incorporated further positively supercoils it, like winding a telephone wire.
1.Ethidium Bromide is used in electrophoresis of DNA fragments because:
[a] It makes the fragments visible under UV light
[b] It makes the DNA fragments more mobile in the gel
[c] It increases the conductivity of electricity through the gel
[d] It helps determine the size of the fragments
Ans. A
Thank you for visiting my blog.Please feel free to share your comment on this article ,Please subscribe and share the articles to get more such articles.
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