Explanation: Topoisomerase functions to untangle the supercoiling of DNA , which is when DNA overwinds into itself. This mechanism facilitates the unwinding action of helicase during replication.
What is the function of topoisomerase?
Topoisomerases catalyze and guide the unknotting or unlinking of DNA by creating transient breaks in the DNA using a conserved tyrosine as the catalytic residue. The insertion of (viral) DNA into chromosomes and other forms of recombination can also require the action of topoisomerases.
What is the function of topoisomerase quizlet?
Topoisomerase breaks covalent bonds in the backbones of both parental strands . Topoisomerase breaks a covalent bond in the backbone of one parental strand. ( Topoisomerase relieves the strain caused by unwinding of the DNA by helicase. First, it binds to the parental DNA ahead of the replication fork.
What is topoisomerase quizlet?
What does topoisomerase 1 solve? Solves the problem caused by tension generated by winding and unwinding processes . It wraps around the DNA and makes a cut allowing the helix to spin. Once relaxed, the strands are reconnected.
What is the function of a topoisomerase in DNA replication quizlet?
What is the purpose of topoisomerase? unwinds the resulting supercoils . What keeps the DNA strands separated during replication? Single Stranded Binding Protein SSBP- which coats the two strands so they will not come back together, protecting them from nuclease attack.
What are the functions of topoisomerase I and II?
Type I topoisomerases relax DNA (i.e., remove supercoils) by nicking and closing one strand of duplex DNA (see Figure 12-14). Type II topoisomerases change DNA topology by breaking and rejoining double-stranded DNA. ... Both replicated circular and linear DNA chromosomes are separated by type II topoisomerases.
What increases positive supercoiling in DNA?
Unwinding of the helix during DNA replication (by the action of helicase) results in supercoiling of the DNA ahead of the replication fork. This supercoiling increases with the progression of the replication fork .
What would happen without topoisomerase?
Topoisomerase alleviates supercoiling downstream of the origin of replication. In the absence of topoisomerase, supercoiling tension would increase to the point where DNA could fragment . DNA replication could not be initiated because there would be no RNA primer. DNA strands would not be ligated together.
What is the difference between helicase and topoisomerase?
The key difference between helicase and topoisomerase is that helicase is an enzyme that separates two complementary strands of DNA by breaking hydrogen bonds between the bases of two strands while topoisomerase is an enzyme that removes positive and negative supercoils formed during the unwinding process of DNA by ...
What is meant by the description antiparallel?
Antiparallel: A term applied to two molecules that are side by side but run in opposite directions . The two strands of DNA are antiparallel.
What is a micelle quizlet?
Micelles are structures composed of a monolayer of amphipathic molecules . ... They are ideally formed by surfactant molecules like detergents, emulsifiers, various wetting agents as well as certain co-polymers. Liposome. They are formed by phospholipid molecules, like lecithin, along with cholesterol.
What does DNA topoisomerase gyrase do quizlet?
DNA gyrase (also referred to as topoisomerase) reduces supercoiling (relaxes tension) which builds up during DNA unwinding, preventing DNA breakage .
Does topoisomerase form phosphodiester bonds?
The enzymes nick a single strand of DNA (pink) and form a phosphodiester bond between the enzyme tyrosine group (Y) and the phosphate group of the DNA. This makes the duplex DNA at the end of the nicking to rotate freely and follow by resealing of the nicking.
What binds Okazaki fragments?
On the lagging strand, DNA synthesis restarts many times as the helix unwinds, resulting in many short fragments called “Okazaki fragments.” DNA ligase joins the Okazaki fragments together into a single DNA molecule.
Which enzyme is used in unwinding of DNA?
During DNA replication, DNA helicases unwind DNA at positions called origins where synthesis will be initiated. DNA helicase continues to unwind the DNA forming a structure called the replication fork, which is named for the forked appearance of the two strands of DNA as they are unzipped apart.
What is the function of Primase?
Primase is an enzyme that synthesizes short RNA sequences called primers . These primers serve as a starting point for DNA synthesis. Since primase produces RNA molecules, the enzyme is a type of RNA polymerase.
