## Restriction Mapping

Genetics as it applies to evolution, molecular biology, and medical aspects.

Agronomy
Garter
Posts: 29
Joined: Wed Jan 17, 2007 5:04 am

### Restriction Mapping

I have this problem for my biology class, and I'm kind of confused.

It says that phage lambda is 48502 base pairs long, and may occur in a linear or circular configuration, depending on the environment. This DNA has 5 recognition sites for the restriction enzyme BAMHI. These sites are located at nucleotide pairs 5505, 22346, 27972, 34499, and 41732, from the 0 end on the molecular map.

IN an experiment, lambda DNA was digested with BAMHI, and the resulting restriction fragments were separated according to their molecular size by agarose gel electrophoresis. The following fragments were observed in the agarose gel: 16841, 12275, 7233m 6527, and 5626 base pairs.

Is the lambda DNA linear or circular in form?

How am i supposed to be able to tell whether it's linear or circular?!?!

canalon
Inland Taipan
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Joined: Thu Feb 03, 2005 2:46 pm
Draw two maps, one circular one linear and place the restriction sites. Calculate for each form the size of the expected fragments...

Or if you do not want to do that tke a rubber band and a piece of string (linear) take a pair of scissors and give the same number of cuts in each (1 is actually enough) count the number of fragments in each case...
Patrick

Science has proof without any certainty. Creationists have certainty without
any proof. (Ashley Montague)

Agronomy
Garter
Posts: 29
Joined: Wed Jan 17, 2007 5:04 am

### okay

okay, I'm confused on how to draw the picture...is it circular?

canalon
Inland Taipan
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Joined: Thu Feb 03, 2005 2:46 pm
Circular for the circular configuration, linear for the linear configuration....
Patrick

Science has proof without any certainty. Creationists have certainty without
any proof. (Ashley Montague)

Agronomy
Garter
Posts: 29
Joined: Wed Jan 17, 2007 5:04 am
okay that's not right, because the question asks "is this lambda DNA in its linear OR circular form? The answer can't be both...

canalon
Inland Taipan
Posts: 3909
Joined: Thu Feb 03, 2005 2:46 pm
Sorry, I did not understand your question. I thought you were referring to the drawing. Which can be both depending on which form you draw, of course.

You say circular, why?
2 good explanations includes:
- Number of fragments (the "cut rubber band experiment") because if it is circular you should have X fragments, if linear X+1 (I hope you see why)

-Size of fragments, if you draw the restriction map. It took me 30s to draw one, since it does not need to be to scale and to estimate the size of the expected fragments in each configuration and compare with the results.
Patrick

Science has proof without any certainty. Creationists have certainty without
any proof. (Ashley Montague)

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