Notes Feb 24 - Notes Feb 24 Today and next time Pg. 51-53,...

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Notes Feb 24 Today and next time Pg. 51-53, 60-65, 872-876 Table 3-2 - Restriction enzymes - Palindrome sequences o Reading 5’ to 3’ on one strand is the same in the other - Arrow cutting in EcoRV makes blunt ends - EcoRI o Held by E.coli - How come restriction enzymes don’t cut their own DNA? o Their own DNA gets methylated - For every restrictin enzyme, there is a corresponding modification methylase which prevents the DNA from cutting its own enzyme - Restriction enzyme is to protect its own DNA by cutting other organism’s DNA (foreign virus, bacteria) - Methylation is to protect its own DNA from the restriction enzyme - This system destroys foreigh DNA containing a recognition site that has not been modified by methylation - The host DNA is always at least half methylated, because although the daughter strand is not methylated until shortly after it is synthesized, the parental strand to which it is paired is already modified (and thus protecets both strand of the DNA from cleavage by the restriction enzyme) o Old strand gets methylated before, which is still enough to protect the new strand from restriction o The new strand will eventually get methylated and offer protection for its daughter strand - Restriction enzymes act much faster; Action of Methylase is slower than restriction enzymes Fig 3-16 - EcoRI and EcoRV cutting sites - Twofold symmetry axis - Complementary sequence is the same if your read both strands from 5’ to 3’ - EcoRI cuts to make sticky ends, 4 bases apart, asymmetrically o Can ligate to any other DNA cut by EcoRI to make recombinant DNA o Under physiological conditions, the base pairs here, which are 2A’s and 2T’s (Four AT base pairs) are melted at 37 degrees because of those nicks, they actually fall apart o If your asked to manipulated molecules that contain a recognition site, you can join that to any other DNA cut by EcoRI to make recombinant DNA, by binding through sticky ends - BamHI and BglII both have the middle four sequence GATC, therefore a BamHI fragment and
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Notes Feb 24 - Notes Feb 24 Today and next time Pg. 51-53,...

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