what is linking number in dna ?

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https://geneticeducation.co.in/dna-topology-what-is-the-linking-number-of-dna

https://geneticeducation.co.in/dna-topology-what-is-the-linking-number-of-dna
DNA Topology- What is the Linking Number of DNA? – Genetic Education
The sum of the total number of twists and writhes are called as a linking number. If both ends of DNA are joined, the linking number remains unchanged, (the linking number is zero in the case of circular DNA molecule). So if we want to change the linking number, we have to break the DNA strand and that function is performed by topoisomerase.

https://biology.stackexchange.com/questions/56700/dna-topology-linking-number-vs-twist

https://biology.stackexchange.com/questions/56700/dna-topology-linking-number-vs-twist
DNA topology Linking number vs twist? – Biology Stack Exchange
The fundamental topological parameter of a covalently closed circular DNA is called the linking number (Lk). Assume that one DNA strand is the edge of an imaginary surface and count the number of times that the other DNA strand crosses this surface (Figure 3).

https://www.oxfordreference.com / display / 10.1093 / oi / authority.20110803100107646

https://www.oxfordreference.com / display / 10.1093 / oi / authority.20110803100107646
Linking number – Oxford Reference
Nov 8, 2023The linking number (L) is determined by the formula: L = W + T. For a relaxed molecule, W = 0, and L = T. The linking number of a closed DNA molecule cannot be changed except by breaking and rejoining of strands.

https://bio.libretexts.org/Bookshelves/Biochemistry/Supplemental_Modules_(Biochemistry)/1:_DNA/1.6:_DNA_Supercoiling_and_Topoisomerases

https://bio.libretexts.org/Bookshelves/Biochemistry/Supplemental_Modules_(Biochemistry)/1:_DNA/1.6:_DNA_Supercoiling_and_Topoisomerases
1.6: DNA Supercoiling and Topoisomerases – Biology LibreTexts
The linking number has not changed, but the length of DNA which contains all the turns is effectively shorter. To maintain 10.6 bp/turn in that region, the DNA will adopt positive supercoils . For example, during the early stages of SV40 replication, the duplex around the origin of replication may initially melt (open up) a region of 750 bases.

https://en.wikipedia.org/wiki/Topoisomerase

https://en.wikipedia.org/wiki/Topoisomerase
Topoisomerase – Wikipedia
The linking number (Lk) describes the number of times that the two single-strands of DNA cross each other in a closed circular DNA molecule. Relaxed DNA molecules have an intrinsic linking number (Lk 0) corresponding to the twisting of the two single-strands around each other in the double helix, approximately once per 10.5 base-pairs (Tw 0 …

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7288220

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7288220
DNA Mechanics and Topology – PMC – National Center for Biotechnology …
A slightly more complicated structure than a single twisted DNA is that of two nicked 4 DNAs wrapped around each other or braided DNAs, such that there is a net inter-DNA linking or catenation number associated with the structure. DNA braids are biologically relevant substrates for type-II topoisomerases, enzymes that manipulate inter- …

https://nap.nationalacademies.org/read/2121/chapter/66

https://nap.nationalacademies.org/read/2121/chapter/66
Dna Geometry and Topology: Linking, Twisting, and Writhing …
The linking number of a DNA, though a topological quantity, can be decomposed into two geometric quantities: writhe Wr and twist Tw, which can be used to describe supercoiling (White, 1969). The linking number is a measure of the crossings seen in any view. These crossings can be divided into two categories, distant crossings, which occur …

https://www.sciencedirect.com/topics/neuroscience/dna-supercoiling

https://www.sciencedirect.com/topics/neuroscience/dna-supercoiling
DNA Supercoiling – an overview | ScienceDirect Topics
The number of times one strand is linked with the other is described by a fundamental property of DNA supercoiling, the linking number (L k). This is related to two geometrical properties of the molecule, the twist ( Tw , rotation of the strands about the helical axis) and the writhe ( Wr , which measures the path of the helix axis in space).

https://bio.libretexts.org/Bookshelves/Genetics/Working_with_Molecular_Genetics_(Hardison)/Unit_I:_Genes_Nucleic_Acids_Genomes_and_Chromosomes/2:_Structures_of_Nucleic_Acids/2.8:_Intro

https://bio.libretexts.org/Bookshelves/Genetics/Working_with_Molecular_Genetics_(Hardison)/Unit_I:_Genes_Nucleic_Acids_Genomes_and_Chromosomes/2:_Structures_of_Nucleic_Acids/2.8:_Intro
2.8: Intro – Biology LibreTexts
Jun 20, 2023L= Linking number= total number of times one strand of the double helix (of a closed molecule) encircles (or links) the other. … Topoisomerases catalyze a change in the linking number of DNA. Topo I = nicking-closing enzyme, can relax positive or negative supercoiled DNA, makes a transient break in 1 strand. …

https://www.genome.gov/about-genomics/fact-sheets/Deoxyribonucleic-Acid-Fact-Sheet

https://www.genome.gov/about-genomics/fact-sheets/Deoxyribonucleic-Acid-Fact-Sheet
Deoxyribonucleic Acid (DNA) Fact Sheet – National Human Genome Research …
Each DNA sequence that contains instructions to make a protein is known as a gene. The size of a gene may vary greatly, ranging from about 1,000 bases to 1 million bases in humans. Genes only make up about 1 percent of the DNA sequence. DNA sequences outside this 1 percent are involved in regulating when, how and how much of a protein is made. lesoutrali bot