Concept explainers
(a)
To describe: The two structural features required by a DNA molecule to maintain a negatively supercoiled state.
Introduction:
Supercoiling is important for packaging of circular DNA molecule referred as closed circular double helix DNA. DNA can be supercoiled in two ways, positive supercoiling and negative supercoiling. Positive supercoiling is the right-handed and double helical form of DNA, while negative supercoiling is the left-handed and double helical form of DNA.
(b)
To enlist: Three structural changes that become more favorable when a DNA molecule is negatively supercoiled.
Introduction:
Deoxyribonucleic acid (DNA) is a genetic material which is responsible for passing information from one generation to another. It is a double helical structure which consists of “two parallel strands” made up of
(c)
To determine: The enzyme that can generate negative superhelicity in DNA with the aid of ATP.
Introduction:
Topoisomerase II or DNA gyrase “reduces supercoiling” in the
(d)
To describe: The physical mechanism by which this enzyme acts.
Introduction:
In replication and transcription, DNA gyrase causes relaxing of positive supercoils and possess the ability to add negative supercoils within the DNA.
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Lehninger Principles of Biochemistry
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