Chromosomal crossover, or crossing over, is the exchange of genetic material during sexual reproduction between two homologous chromosomes' non-sister chromatids that results in recombinant chromosomes. It is one of the final phases of genetic recombination, which occurs in the pachytene stage of prophase I of meiosis during a process called synapsis. Synapsis begins before the synaptonemal complex develops and is not completed until near the end of prophase I. Crossover usually occurs when matching regions on matching chromosomes break and then reconnect to the other chromosome.
RuvABC is a complex of three proteins that mediate branch migration and resolve the Holliday junction created during homologous recombination in bacteria. As such, RuvABC is critical to bacterial DNA repair.
Homologous recombination is a type of genetic recombination in which genetic information is exchanged between two similar or identical molecules of double-stranded or single-stranded nucleic acids.
Cre-Lox recombination is a site-specific recombinase technology, used to carry out deletions, insertions, translocations and inversions at specific sites in the DNA of cells. It allows the DNA modification to be targeted to a specific cell type or be triggered by a specific external stimulus. It is implemented both in eukaryotic and prokaryotic systems. The Cre-lox recombination system has been particularly useful to help neuroscientists to study the brain in which complex cell types and neural circuits come together to generate cognition and behaviors. NIH Blueprint for Neuroscience Research has created several hundreds of Cre driver mouse lines which are currently used by the worldwide neuroscience community.
A Holliday junction is a branched nucleic acid structure that contains four double-stranded arms joined. These arms may adopt one of several conformations depending on buffer salt concentrations and the sequence of nucleobases closest to the junction. The structure is named after Robin Holliday, the molecular biologist who proposed its existence in 1964.
Recombinases are genetic recombination enzymes.
Robin Holliday was a British molecular biologist. Holliday described a mechanism of DNA-strand exchange that attempted to explain gene-conversion events that occur during meiosis in fungi. That model first proposed in 1964 and is now known as the Holliday Junction.
Crossover junction endonuclease EME1 is an enzyme that in humans is encoded by the EME1 gene. It forms a complex with MUS81 which resolves Holliday junctions. In mammalian cells the EME1/MUS81 protein complex is redundant for DNA damage repair with GEN1 endonuclease. In mice, EME1/MUS81 and GEN1 redundantly contribute to Holliday junction processing. When homozygous mutations of Gen1 and Eme1 were combined in mice the result was synthetic lethality at an early embryonic stage. Homozygosity for Gen1 mutations did not cause a DNA repair deficiency in mice. But when mice were both homozygous mutant for Gen1 and also heterozyous for an Emc1 mutation, they showed increased sensitivity to DNA damaging agents. This finding, indicated a redundant role of GEN1 and EME1 in DNA repair. Gen1 and Emc1 were also shown to have redundant roles in meiotic recombination.
Branch migration is the process by which base pairs on homologous DNA strands are consecutively exchanged at a Holliday junction, moving the branch point up or down the DNA sequence. Branch migration is the second step of genetic recombination, following the exchange of two single strands of DNA between two homologous chromosomes. The process is random, and the branch point can be displaced in either direction on the strand, influencing the degree of which the genetic material is exchanged. Branch migration can also be seen in DNA repair and replication, when filling in gaps in the sequence. It can also be seen when a foreign piece of DNA invades the strand.
SLX4 is a protein involved in DNA repair, where it has important roles in the final steps of homologous recombination. Mutations in the gene are associated with the disease Fanconi anemia.
Simon Joseph Boulton is a British scientist who has made important contributions to the understanding of DNA repair and the treatment of cancer resulting from DNA damage. He currently occupies the position of Senior Scientist and group leader of the DSB Repair Metabolism Laboratory at the Francis Crick Institute, London. He is also an honorary Professor at University College London.
Stephen Charles Kowalczykowski is a Distinguished Professor of Microbiology and Molecular Genetics at the University of California at Davis. His research focuses on the biochemistry and molecular biology of DNA repair and homologous recombination. His lab combines fluorescence microscopy, optical trapping and microfluidics to manipulate and visualize single molecules of DNA and the enzymes involved in processing and repairing DNA. He calls this scientific approach, "visual biochemistry". Stephen Kowalczykowski was elected to the American Society for Arts and Science in 2005, the National Academy of Sciences in 2007 and was a Harvey Society Lecturer at Rockefeller University in 2012.
Crossover junction endodeoxyribonuclease, also known as Holliday junction resolvase, Holliday junction endonuclease, Holliday junction-cleaving endonuclease, Holliday junction-resolving endoribonuclease, crossover junction endoribonuclease, and cruciform-cutting endonuclease, is an enzyme involved in DNA repair and homologous recombination. Specifically, it performs endonucleolytic cleavage that results in single-stranded crossover between two homologous DNA molecules at the Holliday junction to produce recombinant DNA products for chromosomal segregation. This process is known as Holliday junction resolution.
Titia de Lange is the Director of the Anderson Center for Cancer Research, the Leon Hess professor and the head of Laboratory Cell Biology and Genetics at Rockefeller University.
SLX4 interacting protein is a protein that in humans is encoded by the SLX4IP gene.
Penelope "Penny" Jeggo is a noted British molecular biologist, best known for her work in understanding damage to DNA. She is also known for her work with DNA gene mutations. Her interest in DNA damage has inspired her to research radiation biology and radiation therapy and how radiation affects DNA. Jeggo has more than 170 publications that pertain to DNA damage, radiation, and cancer research and has received 3 top science awards/medals for her research. Jeggo has also been a member of several organizations that pertain to radiation biology; these organizations include Committee on Medical Aspects of Radiation in the Environment (COMARE), National Institute for Radiation Science laboratory researcher, and the Multidisciplinary European Low Dose Initiative (MELODI). Jeggo is a member of these organizations, and she is also an editor for several publication journals that are related to cancer and radiation biology. Jeggo is very passionate about her research and in an interview with Fiona Watt claimed that “Although my results contributed only the tiniest smidgeon to scientific knowledge, I gained immense satisfaction from it”.
Kalappa Muniyappa is an Indian molecular biologist and geneticist, known for his researches on the chromatization of DNA and gene targeting. He is a professor and chairman of the department of biochemistry of the Indian Institute of Science and an elected fellow of the Indian National Science Academy, Indian Academy of Sciences and the National Academy of Sciences, India. The Council of Scientific and Industrial Research, the apex agency of the Government of India for scientific research, awarded him the Shanti Swarup Bhatnagar Prize for Science and Technology, one of the highest Indian science awards, in 1995, for his contributions to biological sciences.
Cruciform DNA is a form of non-B DNA, or an alternative DNA structure. The formation of cruciform DNA requires the presence of palindromes called inverted repeat sequences. These inverted repeats contain a sequence of DNA in one strand that is repeated in the opposite direction on the other strand. As a result, inverted repeats are self-complementary and can give rise to structures such as hairpins and cruciforms. Cruciform DNA structures require at least a six nucleotide sequence of inverted repeats to form a structure consisting of a stem, branch point and loop in the shape of a cruciform, stabilized by negative DNA supercoiling.
GEN1, Holliday junction 5' flap endonuclease is a protein that in humans is encoded by the GEN1 gene.
John Francis Xavier Diffley is an American biochemist and Associate Research Director at the Francis Crick Institute. He is known for his contributions to the understanding of how DNA replication is initiated, and how it is subsequently regulated throughout the cell cycle and in response to DNA damage.
