DNA restriction map drawing...

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DNA restriction map drawing...

Post by scholesmu » Mon Apr 25, 2011 10:23 pm

1. A 1 in 4 dilution of an overnight culture of E coli has an absorbance (590nm) of 0.25
How much overnight culture must be added to 50ml of fresh medium to give a starting culture with absorbance (590nm) of 0.05?

2. A small DNA molecule was cleaved with a number of different restriction endonucleases and the fragment sizes were determined by gel electrophoresis as shown below.

EcoRI 2.6
BamHI 2.6
PstI 2.6
EcoRI+BamHI 1.3,0.8,0.5
EcoRI+PstI 1.3,0.7,0.6

i can't draw the restriction map...
so confuse why bamHI can cut only 1 alone but 2 when together with EcoRI....

so is it circular or linear fragment?
how could i locate the site unambigously with respect to one anther?
any uncertainty with respect to the map?

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Inland Taipan
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Post by JackBean » Tue Apr 26, 2011 6:50 am

1. the O/N culture has approx. OD590 of 1, so you need to dilute it approx. 20-times. Thus for 50 ml you need to add about 2.5 ml

2. there is obviously some problem, since each RE should cut once (you get only 1 fragment in single restriction), but with two REs you get three fragments...

Cis or trans? That's what matters.

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