Unformatted text preview: eld, and quantum mechanics dictates that the proton can be in one of just two energy levels. The
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interaction of one proton with a typical lab magnetic ﬁeld gives an energy difference of 3.972 x 1025 J between
the two energy levels.
Q2. A (5 points)
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If a sample has a total of 1016 protons, how many will be in the lower energy level at 25° C ? Q2. B (5 points)
The “spin state” of a group of protons in the same molecule can be described by specifying whether each spin
is in the lower energy level, state A, or in the upper energy level, state B. The spins behave independently of
one another (the spin state of one does not depend on the spin states of the others). For a group of six protons
how many distinct states are there? For example, the two spin states ABBABB and AABBBB are two distinct
states, although they have the same energy. Q2. C (5 points)
If we take the probability of a proton being in state A and being in state B each to be exactly 1/2 (i.e. like a coin
ﬂip) so that all possible spin states are equally populated, predict the probability that a group of four protons
has two spins in state A and two in state B. DNA Supercoiling Midterm 2010 Ques;on 2B UC Berkeley, Chem 130/MCB 100A, Fall 2013, Midterm Exam 1. Your Name___________________________ Q1B. (8 points) Consider a circular plasmid DNA that is 3600 base pairs in length.
Assume that in its linear form that the average twist per base pair is 36°.
An image of this DNA from a cell was taken, shown at the right.
For this supercoiled form of the plasmid specify the values of the following
parameters:
(i) Twist (in turns)_________ C (ii) Linking number_________
(iii) Writhe__________
(iv) Assume that the plasmid is relaxed and forms a ﬂat circle. What is the
circumference of the circle? Q1C. 2’3’ dideoxy nucleotide triphosphates are potent inhibitors of DNA replication. Explain why
these molecules block DNA replication. (2 points) UC Berkeley, Chem 130/MCB 100A, Fall 2013, Midterm Exam 1. Your Name___________________________ Q1B. (8 points) Consider a circular plasmid DNA that is 3600 base pairs in length.
Assume that in its linear form that the average twist per base p...
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 Fall '09
 Kuryian
 Proton

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