Information about Genetic Recombination
Genetic recombination is the process by which a strand of DNA is broken and then joined to the end of a different DNA molecule. In eukaryotes recombination commonly occurs during meiosis as chromosomal crossover between paired chromosomes. This process leads to offspring having different combinations of genes from their parents and can produce new chimeric alleles. In evolutionary biology this shuffling of genes is thought to have many advantages, including that of allowing sexually reproducing organisms to avoid Muller's ratchet. However, a recombination pathway in DNA is any way by which a broken DNA molecule is reconnected to form a whole DNA strand.
In molecular biology "recombination" can also refer to artificial and deliberate recombination of disparate pieces of DNA, often from different organisms, creating what is called recombinant DNA.
Enzymes called recombinases catalyze natural recombination reactions. RecA, the recombinase found in E. coli, is responsible for the repair of DNA double strand breaks (DSBs). In yeast and other eukaryotic organisms there are two recombinases required for repairing DSBs. The RAD51 protein is required for mitotic and meiotic recombination and the DMC1 protein is specific to meiotic recombination.
Chromosomal crossover refers to recombination between the paired chromosomes inherited from each of one's parents, generally occurring during meiosis. During prophase I the four available chromatids are in tight formation with one another. While in this formation, homologous sites on two chromatids can mesh with one another, and may exchange genetic information.
Because recombination can occur with small probability at any location along chromosome, the frequency of recombination between two locations depends on their distance. Chromosomes are expected to cross over at many points along their length; for genes sufficiently distant on the same chromosome the amount of crossover is so high that these genes effectively assort independently.
In conservative site-specific recombination, a mobile DNA element is inserted into a strand of DNA by means similar to that seen in crossover. A segment of DNA on the mobile element matches exactly with a segment of DNA on the target, allowing enzymes called integrases to insert the rest of the mobile element into the target. Integrases are a special type of Recombinases. Recombinases are enzymes which cleave the double stranded DNA at specific sites resulting in a loss of the Phosphodiester bonds. This reaction is stabilised by the formation of a covalent bond between the Recombinase and the DNA through a Phospho Tyrosine Bond.
Recombination between DNA sequences that contain no sequence homology, also referred to as nonhomologous end joining.
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In molecular biology "recombination" can also refer to artificial and deliberate recombination of disparate pieces of DNA, often from different organisms, creating what is called recombinant DNA.
Enzymes called recombinases catalyze natural recombination reactions. RecA, the recombinase found in E. coli, is responsible for the repair of DNA double strand breaks (DSBs). In yeast and other eukaryotic organisms there are two recombinases required for repairing DSBs. The RAD51 protein is required for mitotic and meiotic recombination and the DMC1 protein is specific to meiotic recombination.
Chromosomal crossover
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Thomas Hunt Morgan's illustration of crossing over (1916)
Because recombination can occur with small probability at any location along chromosome, the frequency of recombination between two locations depends on their distance. Chromosomes are expected to cross over at many points along their length; for genes sufficiently distant on the same chromosome the amount of crossover is so high that these genes effectively assort independently.
Conservative site-specific recombination
In conservative site-specific recombination, a mobile DNA element is inserted into a strand of DNA by means similar to that seen in crossover. A segment of DNA on the mobile element matches exactly with a segment of DNA on the target, allowing enzymes called integrases to insert the rest of the mobile element into the target. Integrases are a special type of Recombinases. Recombinases are enzymes which cleave the double stranded DNA at specific sites resulting in a loss of the Phosphodiester bonds. This reaction is stabilised by the formation of a covalent bond between the Recombinase and the DNA through a Phospho Tyrosine Bond.
Transpositional recombination
Another form of site-specific recombination, transpositional recombination does not require an identical strand of DNA in the mobile element to match with the target DNA. Instead, the integrases involved introduce nicks in both the mobile element and the target DNA, allowing the mobile DNA to enter the sequence. The nicks are then removed by ligases.Nonhomologous recombination
Recombination between DNA sequences that contain no sequence homology, also referred to as nonhomologous end joining.
See also
External links
- The Holliday Model of Genetic Recombination
- MeSH Genetic+recombination
- Animated guide to homologous recombination.
References
- Alberts, B. et al., Molecular Biology of the Cell, 3rd Edition. Garland Publishing, 1994.
- Mayerhofer R, Koncz-Kalman Z, Nawrath C, Bakkeren G, Crameri A, Angelis K, Redei GP, Schell J, Hohn B, Koncz C. T-DNA integration: a mode of illegitimate recombination in plants. EMBO J. 1991 Mar;10(3):697-704.
Genetics: genetic recombination |
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meiosis (IPA: /maɪˈəʊsɪs/) is the process by which one diploid eukaryotic cell divides to generate four haploid cells often called gametes.
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Chromosomal crossover (or crossing over) is the process by which two chromosomes, paired up during prophase 1 of meiosis, exchange some portion of their DNA. Crossing over is specifically initiated in pachytene, before the synaptonemal complex develops, and is not completed
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For the hard rock band, see .
An allele (Pronounced: /əˈlil/) is a viable DNA (deoxyribonucleic acid) coding that occupies a given locus (position) on a chromosome...... Click the link for more information.
In evolutionary genetics, Muller's ratchet (named after Hermann Joseph Muller and a mechanical device) is the name given to the process by which the genomes of an asexual population accumulate deleterious mutations in an irreversible manner.
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Molecular biology is the study of biology at a molecular level. The field overlaps with other areas of biology and chemistry, particularly genetics and biochemistry. Molecular biology chiefly concerns itself with understanding the interactions between the various systems of a cell,
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Recombinant DNA is a form of artificial DNA which is engineered through the combination or insertion of one or more DNA strands, thereby combining DNA sequences which would not normally occur together.
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Enzymes are proteins that catalyze (i.e. accelerate) chemical reactions.[1] In enzymatic reactions, the molecules at the beginning of the process are called substrates, and the enzyme converts them into different molecules, the products.
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Recombinases, genetic recombination enzymes [1], can refer to:
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- Cre recombinase
- Hin recombinase
- RecA/RAD51
References
1. ^ MeSH Recombinases
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catalysis is the acceleration (increase in rate) of a chemical reaction by means of a substance called a catalyst, which is itself not consumed by the overall reaction.
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Reca is a village and municipality in western Slovakia in Senec District in the Bratislava Region.
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History
In historical records the village was first mentioned in 1256.Geography
The municipality lies at an altitude of 124 metres and covers an area of 9.921km²...... Click the link for more information.
E. coli
Binomial name
Escherichia coli
(Migula 1895)
Castellani and Chalmers 1919
Escherichia coli (IPA: [ˌɛ.
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Binomial name
Escherichia coli
(Migula 1895)
Castellani and Chalmers 1919
Escherichia coli (IPA: [ˌɛ.
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Rad51 is the eukaryotic homolog of the prokaryotic RecA protein. It is well conserved from yeast to humans.
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Function
In humans, Rad51 is a 339-amino acid protein that plays a major role in homologous recombination of DNA during double strand break repair...... Click the link for more information.
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meiosis (IPA: /maɪˈəʊsɪs/) is the process by which one diploid eukaryotic cell divides to generate four haploid cells often called gametes.
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Chromosomal crossover (or crossing over) is the process by which two chromosomes, paired up during prophase 1 of meiosis, exchange some portion of their DNA. Crossing over is specifically initiated in pachytene, before the synaptonemal complex develops, and is not completed
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Figure 1: A representation of a condensed eukaryotic chromosome, as seen during cell division.]] A chromosome is a single large macromolecule of DNA, and constitutes a physically organized form of DNA in a cell.
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meiosis (IPA: /maɪˈəʊsɪs/) is the process by which one diploid eukaryotic cell divides to generate four haploid cells often called gametes.
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chromatid is one of two identical strands of DNA making up a chromosome that are joined at their centromeres, for the process of nuclear division (mitosis or meiosis). The term is used so long as the centromeres remain in contact.
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In evolutionary biology, homology is any similarity between characters that is due to their shared ancestry. There are examples in different branches of biology. Anatomical structures that perform the same function in different biological species and evolved from the same structure
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Genetic linkage occurs when particular genetic loci or alleles for genes are inherited jointly. Genetic loci on the same chromosome are physically connected and tend to segregate together during meiosis, and are thus genetically linked.
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In genetics, Independent assortment is the process of random segregation and assortment of chromosomes during gametogenesis to produce genetically unique gametes. Independent assortment occurs during meiosis I in eukaryotic organisms, specifically anaphase I of meiosis
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Site-specific recombination
In site-specific-recombination, DNA strand exchange takes place between segments possessing only a limited degree of sequence homology (Kolb 2002; Coates et al., 2005)...... Click the link for more information.
Site-specific recombination
In site-specific-recombination, DNA strand exchange takes place between segments possessing only a limited degree of sequence homology (Kolb 2002; Coates et al., 2005)...... Click the link for more information.
In biochemistry, a ligase (from the Latin verb ligāre — "to bind" or "to glue together") is an enzyme that can catalyse the joining of two large molecules by forming a new chemical bond, usually with accompanying hydrolysis of a small chemical group pendant to
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Non-homologous end joining (NHEJ) is a pathway that can be used to repair double-strand breaks in DNA. NHEJ is referred to as "non-homologous" because the break ends are directly ligated without the need for a homologous template, in contrast to homologous recombination,
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In evolutionary biology, homology is any similarity between characters that is due to their shared ancestry. There are examples in different branches of biology. Anatomical structures that perform the same function in different biological species and evolved from the same structure
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Non-homologous end joining (NHEJ) is a pathway that can be used to repair double-strand breaks in DNA. NHEJ is referred to as "non-homologous" because the break ends are directly ligated without the need for a homologous template, in contrast to homologous recombination,
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Genetic linkage occurs when particular genetic loci or alleles for genes are inherited jointly. Genetic loci on the same chromosome are physically connected and tend to segregate together during meiosis, and are thus genetically linked.
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