What is the function of Holliday junction?
Holliday junction, cross-shaped structure that forms during the process of genetic recombination, when two double-stranded DNA molecules become separated into four strands in order to exchange segments of genetic information.
What is a Holliday junction in biology?
Holliday junctions are intermediates of homologous recombination in which two homologous DNA duplexes are joined by the interchange of a pair of (nearly) identical single strands.
What is Holliday model of recombination?
The Holliday model for homologous recombination Single-strand nicks are introduced at the same position on both parental molecules. The nicked strands then exchange by complementary base pairing, and ligation produces a crossed-strand intermediate called a Holliday junction.
What does the resolution of Holliday junctions mean?
Holliday junction (HJ) resolution is essential for chromosome segregation at meiosis and the repair of stalled/collapsed replication forks in mitotic cells. All organisms possess nucleases that promote HJ resolution by the introduction of symmetrically related nicks in two strands at, or close to, the junction point.
Which DNA is connected by Holliday junction?
Holliday junctions provide a covalent link between recombining DNA molecules and need to be removed prior to chromosome segregation at mitosis. Defects in their resolution lead to mitotic catastrophe, characterized by the formation of DNA breaks and chromosome aberrations.
What are the steps of Holliday junction formation?
Several of the individual steps that constitute the Holliday model have been demonstrated to occur in vivo or in vitro, such as nicking, strand displacement, branch migration, repair synthesis, and ligation.
How do you resolve Holliday junction?
Cleavage, or resolution, of the Holliday junction can occur in two ways. Cleavage of the original set of strands leads to two molecules that may show gene conversion but not chromosomal crossover, while cleavage of the other set of two strands causes the resulting recombinant molecules to show crossover.
Which enzyme is important in the resolution of a Holliday junction?
Hallmark Characteristics. Holliday junction cleavage, which generates two unconnected DNA duplexes, is catalyzed by a group of structure-selective endonucleases called HJ resolvases.
How do you resolve a Holliday junction?
Which proteins are required for resolution of Holliday junction?
RuvC is a dimeric protein that promotes HJ resolution by introducing a pair of symmetrically related nicks in two strands that lie diametrically opposed across the junction point.
Which nuclease is responsible resolution of Holliday junction?
Holliday junction cleavage, which generates two unconnected DNA duplexes, is catalyzed by a group of structure-selective endonucleases called HJ resolvases. These nucleases have been isolated from bacteria, bacteriophages, archaea, viruses, yeasts, plants, and mammals (Table 1) and share a number of common properties.
Which proteins are required for the resolution of Holliday junction?
Why are Holliday junctions a central intermediate in homologous recombination?
Holliday junctions have been considered a central intermediate in homologous recombination ever since Robin Holliday proposed their existence and suggested that crossovers result from their resolution .
How are chromosomes broken in the Holliday model?
If the crossed strands are cleaved by endonucleases, the after ligation within the chromosomes there will be two the chromosomes there will be two non recombinant chromosome with short heteroduplex regions. Alternatively if one rotates on DNA helix 180 0, a process called isomerisation, we can visualise how un crossed strands can be broken.
Which is heterodimer promotes Holliday junction resolution?
The MLH1-MLH3 heterodimer promotes the formation of crossover recombinants. While the other three pathways, involving proteins MUS81 -MMS4, SLX1 and YEN1, respectively, can promote Holliday junction resolution in vivo, absence of all three nucleases has only a modest impact on formation of crossover products.
Which is responsible for meiotic crossover in fission yeast?
The heterodimeric nuclease Mus81–Eme1 has been proposed to be a Holliday junction resolvase and has now been found to be responsible for nearly all meiotic crossovers in fission yeast.