1. What is the superhelical density (o) of a closed-circular DNA with a length of 4,200 bp and a linking number (Lk) of 374? What is the superhelical density (o) of the same DNA when Lk = 412? In each case, is the DNA negatively or positively supercoiled?

Biochemistry
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Chapter1: Biochemistry: An Evolving Science
Section: Chapter Questions
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Question1
ustify
S
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2
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j
1. What is the superhelical density (o) of a closed-circular DNA with a length of 4,200 bp and a linking
number (Lk) of 374? What is the superhelical density (a) of the same DNA when Lk = 412? In each
case, is the DNA negatively or positively supercoiled?
4
all answers!
2. The complete genome of the simplest bacterium known, Mycoplasma genitalium, is a circular DNA
molecule with 580,070 bp. Calculate the molecular weight (assume the molecular weight of a
nucleotide pair is 650 g/mol) and contour length (when relaxed) of this molecule. What is Lko for this
Mycoplasma chromosome?
3. The T4-like bacteriophage JS98 has a DNA of molecular weight 1.11 x 108 grams/mole (g/mol)
contained in a head about 100 nanometers (nm) long.
(a) Calculate the length of the DNA molecule (assume the molecular weight of a nucleotide pair is 650
g/mol) and compare it with the length of the JS98 head.
(b) Consult the online database Genome (https://www.ncbi.nlm.nih.gov/data-hub/genome/). What is
the exact number of base pairs in the JS98 genome? Provide a citation (make sure it follows the
exact format as described in the Biology Style Manual).
4. A closed-circular DNA molecule in its relaxed form has an Lk of 500. Approximately how many base
pairs are in this DNA? How does the Lk change (increases, decreases, does not change, becomes
undefined) in each of the following situations?
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(a) A protein complex binds, wrapping the DNA round it to form a solenoidal supercoil.
(b) One DNA strand is broken.
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D
#
(c) DNA gyrase and ATP are added to the DNA in solution.
(d) The double helix is denatured by heat.
B
C
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Transcribed Image Text:ustify S W 2 X j 1. What is the superhelical density (o) of a closed-circular DNA with a length of 4,200 bp and a linking number (Lk) of 374? What is the superhelical density (a) of the same DNA when Lk = 412? In each case, is the DNA negatively or positively supercoiled? 4 all answers! 2. The complete genome of the simplest bacterium known, Mycoplasma genitalium, is a circular DNA molecule with 580,070 bp. Calculate the molecular weight (assume the molecular weight of a nucleotide pair is 650 g/mol) and contour length (when relaxed) of this molecule. What is Lko for this Mycoplasma chromosome? 3. The T4-like bacteriophage JS98 has a DNA of molecular weight 1.11 x 108 grams/mole (g/mol) contained in a head about 100 nanometers (nm) long. (a) Calculate the length of the DNA molecule (assume the molecular weight of a nucleotide pair is 650 g/mol) and compare it with the length of the JS98 head. (b) Consult the online database Genome (https://www.ncbi.nlm.nih.gov/data-hub/genome/). What is the exact number of base pairs in the JS98 genome? Provide a citation (make sure it follows the exact format as described in the Biology Style Manual). 4. A closed-circular DNA molecule in its relaxed form has an Lk of 500. Approximately how many base pairs are in this DNA? How does the Lk change (increases, decreases, does not change, becomes undefined) in each of the following situations? w $ 3 (a) A protein complex binds, wrapping the DNA round it to form a solenoidal supercoil. (b) One DNA strand is broken. E D # (c) DNA gyrase and ATP are added to the DNA in solution. (d) The double helix is denatured by heat. B C $ 4 R F F4 V % 5 FS T G B ^ 6 FG Y H & 7 U N PrtScn J * 8 Home 1 M ( 9 K End O V O L PgUp P - A PgDn Alt ¡
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