1) why do we use the CTAB in DNA extraction lab? what is the purpose? 2) why do we use the ethanol? what is the purpose? Solution a) It is a cationic surfactant. Its uses include providing a buffer solution for the extraction of DNA.We use this method for extracting genome sequencing quality (i.e. unsheared) DNA that can be used for large insert libraries. Because of the broad distribution of negative charges in glycoproteins, these form broad, fuzzy bands in SDS-PAGE (Laemmli-electrophoresis). This can be avoided by using positively charged detergents like CTAB instead of the negatively charged SDS. Proteins can be blotted from CTAB-gels in analogy to western blots , and CTAB-PAGE can be used as second dimension after IEF. b) Ethanol or isopropyl alcohol causes the DNA to precipitate. When DNA comes out of solution it tends to clump together, which makes it visible. The long strands of DNA will wrap around the stirrer or transfer pipet when it is swirled at the interface between the two layers. .

1. 1) why do we use the CTAB in DNA extraction lab? what is the purpose?
2) why do we use the ethanol? what is the purpose?
Solution
a) It is a cationic surfactant. Its uses include providing a buffer solution for the extraction of
DNA.We use this method for extracting genome sequencing quality (i.e. unsheared) DNA that
can be used for large insert libraries.
Because of the broad distribution of negative charges in glycoproteins, these form broad, fuzzy
bands in SDS-PAGE (Laemmli-electrophoresis). This can be avoided by using positively
charged detergents like CTAB instead of the negatively charged SDS. Proteins can be blotted
from CTAB-gels in analogy to western blots , and CTAB-PAGE can be used as second
dimension after IEF.
b) Ethanol or isopropyl alcohol causes the DNA to precipitate. When DNA comes out of solution
it tends to clump together, which makes it visible. The long strands of DNA will wrap around the
stirrer or transfer pipet when it is swirled at the interface between the two layers.