11 public questions tagged with this topic.
Helicase unwinds the DNA double helix, allowing replication to proceed. This follows from NCERT principle where relation explains outcome clearly for students.
Ref: NCERT Biology Textbook for Class XI and XII (Botany section), Chapter: Biology - Botany portion covering relevant concept, Topic: Plant structure, physiology and applications.
Authentic initiation of DNA synthesis requires coordinated activation of MCM2-7 helicase loaded at licensed origins. Two S-phase kinases perform this: Cdc7-Dbf4 complex called DDK phosphorylates N-terminal tails of MCM2, MCM4 and MCM6 promoting Cdc45 recruitment, while CDK2-Cyclin E and CDK2-Cyclin A phosphorylate Treslin, Ticrr, RecQL4 and TopBP1 creating phospho-binding sites for assembling replication machinery including Cdc45-MCM-GINS active helicase and Pol epsilon recruitment. Entry dataset incorrectly lists p53 as initiating kinase; biologically p53 acts opposite as genome guardian. Upo
Ref: Labib, Mechanism of DNA Replication Initiation by DDK and CDK, Science 2010; NCBI Bookshelf, Regulation of Origin Firing by CDK2.
Helicase unwinds the DNA double helix, allowing replication and transcription to occur.
Ref: NCERT Class 12 Biology Chapter 9: Biotechnology: Principles and Processes Tools - Restriction Enzymes - Molecular Scissors
Topoisomerase relieves supercoiling tension in DNA by cutting and rejoining strands.
Ref: NCERT Class 12 Biology Chapter 5: Molecular Basis of Inheritance DNA Replication - Semiconservative and Machinery
Helicase unwinds the DNA double helix at the replication fork, allowing replication to proceed.
Ref: NCERT Class 12 Biology Chapter 5: Molecular Basis of Inheritance DNA Replication - Semiconservative and Machinery
Helicase unwinds the DNA double helix, allowing replication to proceed.
Ref: NCERT Class 12 Biology Chapter 5: Molecular Basis of Inheritance DNA Structure Double Helix and Packaging - Nucleosome
Helicase unwinds the DNA double helix, allowing replication to proceed.
Ref: NCERT Class 11 Biology Chapter 9: Biomolecules Enzymes - Properties Classification and Cofactors
Among general Pol II factors, TFIIH alone possesses ATP-dependent DNA helicase activity essential for promoter opening. Complex composed of ten subunits includes XPB ERCC3 translocase with 3' to 5' helicase that pumps downstream DNA toward polymerase, generating torsional stress to melt eleven to fifteen base pairs around transcription start site. XPD ERCC2 helicase participates primarily in nucleotide excision repair. Helicase action requires ATP hydrolysis and is inhibited by triptolide anticancer drug. TFIIH entry after Pol II-TFIIF completes preinitiation complex assembly enabling open com
Ref: Lodish et al., Molecular Cell Biology, 9th ed., Chapter 10: TFIIH helicase melts promoter DNA; Alberts 7th ed., General transcription factors TFIIH function
Following MutH nicking of daughter strand at hemimethylated GATC, intervening DNA between nick and mismatch must be unwound and removed. Helicase II, named UvrD, is recruited through direct protein interaction with MutL. Using ATP hydrolysis, UvrD translocates 3' to 5' direction, unwinding duplex flanking mismatch region. Single-stranded DNA binding protein stabilizes exposed strands preventing reannealing. Subsequently, appropriate exonucleases degrade unwound strand: 3' to 5' exonucleases if nick is upstream, 5' to 3' RecJ if nick downstream. DNA polymerase III then fills gap accurately.
Ref: Watson et al., Molecular Biology of the Gene, 7th ed., Chapter 10: MMR excision helicase UvrD role; Alberts Ch.5 Exonucleolytic removal
Double Holliday junctions arising during DSBR can yield crossover if cleaved by resolvases such as Mus81 or Yen1. Somatic cells limit crossovers to avoid loss of heterozygosity and translocations. RecQ helicase family members including yeast Sgs1 and human BLM cooperate with topoisomerase IIIα and Rmi1/Rmi2 to dissolve double Holliday junctions. Helicase migration converges junctions into single hemicatenane structure decatenated by topoisomerase. This dissolution pathway produces exclusively non-crossover products, preventing interchange of flanking markers, while resolution by structure-spec
Ref: Alberts et al., Molecular Biology of the Cell, 7th ed., Chapter 5: RecQ Helicase Dissolution Preventing Crossovers
Bidirectional unwinding of parental duplex at bacterial replication fork requires hexameric helicase DnaB encircling lagging strand template and moving 5' to 3' direction using ATP hydrolysis energy. DnaB disrupts base pairing ahead of polymerase generating single-stranded templates for both leading and lagging synthesis simultaneously. Activity stimulated by DnaC loader during initiation and by tau subunit and SSB during elongation. DnaA protein recognizes oriC boxes but does not unwind long stretches, while DnaG synthesizes RNA primers after unwinding provides single-stranded regions.
Ref: NCBI Bookshelf, Molecular Genetics: E. coli DnaB hexameric helicase mechanism and polarity
