Biological Sciences
Genetic Recombination
Genetic recombination is the process by which genetic material is exchanged between different organisms or different regions within the same organism's DNA. This can occur through processes such as crossing over during meiosis or horizontal gene transfer in bacteria. Genetic recombination plays a key role in generating genetic diversity and is important for evolution and adaptation in populations.
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10 Key excerpts on "Genetic Recombination"
eBook - ePubAdvanced Molecular Biology
A Concise Reference
- Richard Twyman(Author)
- 2018(Publication Date)
- Garland Science(Publisher)
Chapter 25Recombination
Fundamental concepts and definitions- Recombination is any process generating new combinations of preexisting genetic material. Intermolecular or interchromosomal recombination generates new combinations by mixing discrete chromosomes (independent assortment of eukaryotic chromosomes at meiosis, and reassortment of segmented viral genomes), whereas intramolecular or intrachromosomal recombination is an enzyme-dependent process where new combinations of genetic material arise by cutting and joining DNA. There are five types of intramolecular recombination (Table 25.1 ), although the molecular reactions — cleaving DNA, exchange of strands between duplexes, DNA repair and resolution — are similar in each case.
- Recombination and mutation are regarded as two discrete mechanisms of genetic change: recombination rearranges information already present, and mutation introduces new information to the genome. Although these are useful definitions, mutation and recombination are intertwined at the molecular level. Many recombination events (especially transposition and illegitimate recombination) cause gene disruption and are described as mutations. Conversely, recombination is required to repair potentially mutagenic or lethal DNA lesions.
- Recombination is exploited in two ways: to map genetic loci and to manipulate genes and genomes. Genetic mapping works on the principle that the further apart two loci lie on the chromosome, the more likely it is that a homologous recombination event will occur between them. Therefore, the proportion of recombinant products of a given cross provides an estimate of physical distance (see Gene Structure and Mapping). Homologous recombination is also exploited for gene targeting, whereas site-specific recombination facilitates inducible deletion and chromosome rearrangement. Transposition and illegitimate recombination are also exploited, and can be used for gene transfer and integration (see
eBook - PDF- K Low(Author)
- 2012(Publication Date)
- Academic Press(Publisher)
THE RECOMBINATION OF GENETIC MATERIAL 1. Genetic Recombination: A Brief Overview K. Brooks Low Radiobiology Laboratories, Yale University School of Medicine, New Haven, Connecticut 06510 I. What is Genetic Recombination? 1 II. What Are the Major Types of Recombination? 4 A. Homologous 4 B. Site-Specific 5 C. Transpositional 5 D. Irregular 8 III. How Is Recombination Detected? 8 IV. How Often Does Recombination Occur, and How Long Does It Take? 9 V. What Length of DNA Can Be Involved in a Recombination Event, and How Much Is Necessary? Π VI. What Indicates That Recombination Is Not Simple? 12 VII. How Is Recombination Important for Cellular Behavior? 14 A. Recombination to Control Genes 14 B. Recombination, Replication, and Repair 14 C. Recombination for Genetic Diversity during Development 15 D. Recombination and Disease 15 E. Recombination and Evolution 15 VIII. A Recombination Bibliography 17 References 18 I. What Is Genetic Recombination? These cases of novelties resulting through a re-combination of the factors brought in by the original pure types are striking because it is not at first sight evident how the novelty has been produced. Generally speaking, however, the re-combinations form in F 2 a series of types many of which are obviously new combinations of features which could be recognized on inspection as present in the pure parents. W. Bateson (1909) Today there are two distinct but related meanings of the term recombi-nation in common usage by geneticists. In the quote above, Bateson introduced the term re-combination as he was summarizing the effects of independent segregation of several differing parental traits of sweet peas into descendants which showed any of a number of possible combinations of traits from the parents. This process of independent ι Copyright © 1988 by Academic Press, Inc. All rights of reproduction in any form reserved.
eBook - PDF- Anatoly Ruvinsky(Author)
- 2009(Publication Date)
- CRC Press(Publisher)
41 three chapter Recombination and randomness The combination rule is confined by the strange phenomenon that Morgan calls crossing-over or the exchange of genes, which he imagines as a real exchange of parts between the chromosomes. … A German scientist has appropriately compared this to the astronomical calculation of celestial bodies still unseen but later on found by the tube—but he adds: Morgan’s predictions exceed this by far, because they mean something principally new, something that has not been observed before. Presentation speech by the Nobel Committee (1933) What is recombination? In this chapter we shall discuss very different biological processes which have at least one common feature: recombination of DNA molecules. Two DNA molecules, if broken, can rejoin. It serves at least two purposes: repair and production of novel DNA molecules which might carry new genetic information. This is the essence of recombination, an ubiquitous and ancient genetic process. There are several types of recombination and only some of them will be considered briefly in this chapter. The major dif-ferences in recombination are between prokaryotes (i.e. bacteria), which have simple cells without a nucleus and a single primitive chromosome, and eukaryotes with highly structured cells and complex chromosomes (i.e. plants and animals). Chromosome recombination in eukaryotes can occur either in mitosis or meiosis. Mitosis is the typical division of eukaryotic somatic cell. It includes a number of consecutive steps, two of which are of particular importance. One of them is replication of chromosomes, which formally is not a part of the mitotic process itself, but absolutely necessary for mitosis to proceed (Figure 3.1). The second step is segregation of replicated chromosomes, called sister chromatids, during which they move to opposite poles.
eBook - ePubRecombinant DNA and Genetic Experimentation
Proceedings of a Conference on Recombinant DNA, Jointly Organised by the Committee on Genetic Experimentation (COGENE) and the Royal Society of London, Held at Wye College, Kent, UK, 1-4 April, 1979
- Joan Morgan, W. J. Whelan(Authors)
- 2013(Publication Date)
- Pergamon(Publisher)
a priori designs. It leads to a somewhat messy continuing patching up of existing systems, taking advantage of duplications, which increase the amount of available genetic material, to develop new functions. If new proteins can be produced from duplicated nucleotide sequences that are translated in a different reading frame, as seems likely, these will have little, if any, relationship to their immediate evolutionary precursors and so their initial functions may be carried out extremely inefficiently. The genetic system has built into it extensive redundancy, which provides both resilience in the face of unwanted variation and a source of material for new developments, as needed. There are no opportunities for neat reconstructions of the genotype in order to clear away the accumulated messy patches.SEX AND RECOMBINATION
Early primitive organisms must, of course, have reproduced asexually. In an asexual population two different advantageous mutations can only be incorporated into a single individual, and so into the population, if one of the mutations occurs in a descendant of an individual in which the other has occurred. In a sexual population, on the other hand, two mutations can be brought together in the same individual by recombination, interpreted in the broadest sense. Thus, as clearly pointed out by Fisher and Muller in the 1930s, sexual reproduction greatly accelerates the rate of evolution by facilitating the accumulation in a single individual of different independently occurring advantageous mutations. This feature of sexual reproduction is undoubtedly responsible for its evolution. As Muller (1958) aptly put it, the difference between asexual and sexual evolution is essentially a contrast between evolution in series as compared to evolution in parallel.Sexual mechanisms, and genetic exchange, comprise two very different and quite separate processes. First, there is the mechanism by which different individuals or organisms, get together and in some way juxtapose their genetic information so that it can be reassorted, or exchanged. In classical genetic terms this includes all those aspects of the sexual process which lead up to synapsis, namely the pairing of chromosomes in meiosis. The second component which is much more specific, is the actual exchange of genetic information at the chromosomal level. Genetic Recombination and reassortment can occur in the absence of recombination in this second more restricted sense. Thus, the independent segregation of whole chromosomes during meiosis is an important part of the process of genetic exchange and recombination from an evolutionary point of view. There are mechanisms of genetic exchange which do not even go as far as synapsis, but involve only whole genetic units or chromosomes. In bacteria, for example, this would include transfer of drug resistance factors. Somatic cell fusion is another process leading to genetic assortment which involves no recombination between homologous chromosomes. It is indeed tempting to speculate that cell fusion and hybridisation, accompanied by more or less erratic chromosomal segregation, may have been the precursor of an organised meiosis in primitive unicellular eukaryotic organisms. Such fusions could have led to evolutionarily effective recombination of genetic information by segregation of whole chromosomes (and also possibly chromosome fragments), before the evolution of precise pairing and recombination between homologous chromosomes (Bodmer, 1972
No longer available |Learn more- (Author)
- 2014(Publication Date)
- Academic Studio(Publisher)
________________________ WORLD TECHNOLOGIES ________________________ Chapter- 14 Homologous Recombination Figure 1. During meiosis, homologous recombination can produce new combinations of genes as shown here between similar but not identical copies of human chromosome 1. ________________________ WORLD TECHNOLOGIES ________________________ Homologous recombination is a type of Genetic Recombination in which nucleotide sequences are exchanged between two similar or identical molecules of DNA. It is most widely used by cells to accurately repair harmful breaks that occur on both strands of DNA, known as double-strand breaks. Homologous recombination also produces new combinations of DNA sequences during meiosis, the process by which eukaryotes make gamete cells, like sperm and egg cells in animals. These new combinations of DNA represent genetic variation in offspring, which in turn enables populations to adapt during the course of evolution. Homologous recombination is also used in horizontal gene transfer to exchange genetic material between different strains and species of bacteria and viruses. Although homologous recombination varies widely among different organisms and cell types, most forms of it involve the same basic steps. After a double-strand break occurs, sections of DNA around the 5' ends of the break are cut away in a process called resection . In the strand invasion step that follows, an overhanging 3' end of the broken DNA molecule then invades a similar or identical DNA molecule that is not broken. After strand invasion, one or two cross-shaped structures called Holliday junctions connect the two DNA molecules. Depending on how the two junctions are cut by enzymes, the type of homologous recombination that occurs in meiosis results in either chromosomal crossover or non-crossover.
eBook - PDF- Arnold W. Ravin, Alvin Nason(Authors)
- 2013(Publication Date)
- Academic Press(Publisher)
140 IV. Mutation and Recombination emphasize that the copy-choice and breakage-reunion mechanisms are not mutually exclusive, and that recombina-tion therefore could involve both processes in the living organism. Finally, the experimental findings do not shed enough light on the question of whether double-stranded or single-stranded DNA molecules are engaged in the phenomenon of recombination. Nevertheless, the kinds of experiments described in this section point the way to further experimental attacks on the problem, for they indicate the restricted conditions under which recombina-tion does occur and so prescribe the design of future ex-periments. The Anomalies of Molecular Recombination An understanding of molecular recombination is of inter-est not only in its own right, but also for what it could tell us about Genetic Recombination occurring at higher levels of biological organization. It is not certain that the recombi-nation that occurs within chromosomes of higher organisms is simply the reflection of recombination occurring between the DNA's of which they are composed. Just as it is possible to imagine that more than one mechanism of molecular re-combination may operate, it is conceivable that the recombi-nation of DNA is but one aspect of chromosomal recombina-tion. This question will receive fuller consideration in the final chapter. At the present time, we might consider whether recombination occurring at the molecular level ex-hibits unique features, properties that are not associated with chromosomal recombination. At least three such properties are worth mentioning here. In classical studies of chromosomal recombination, it was regularly noted that the more distant two genes were to each other, the more frequent were multiple exchanges be-tween their sites.
No longer available |Learn more- (Author)
- 2014(Publication Date)
- Research World(Publisher)
________________________ WORLD TECHNOLOGIES ________________________ Chapter- 8 Homologous Recombination Figure 1. During meiosis, homologous recombination can produce new combinations of genes as shown here between similar but not identical copies of human chromosome 1. ________________________ WORLD TECHNOLOGIES ________________________ Homologous recombination is a type of Genetic Recombination in which nucleotide sequences are exchanged between two similar or identical molecules of DNA. It is most widely used by cells to accurately repair harmful breaks that occur on both strands of DNA, known as double-strand breaks. Homologous recombination also produces new combinations of DNA sequences during meiosis, the process by which eukaryotes make gamete cells, like sperm and egg cells in animals. These new combinations of DNA represent genetic variation in offspring, which in turn enables populations to adapt during the course of evolution. Homologous recombination is also used in horizontal gene transfer to exchange genetic material between different strains and species of bacteria and viruses. Although homologous recombination varies widely among different organisms and cell types, most forms of it involve the same basic steps. After a double-strand break occurs, sections of DNA around the 5' ends of the break are cut away in a process called resection . In the strand invasion step that follows, an overhanging 3' end of the broken DNA molecule then invades a similar or identical DNA molecule that is not broken. After strand invasion, one or two cross-shaped structures called Holliday junctions connect the two DNA molecules. Depending on how the two junctions are cut by enzymes, the type of homologous recombination that occurs in meiosis results in either chromosomal crossover or non-crossover.
eBook - ePub- Subrata Pal(Author)
- 2019(Publication Date)
- Academic Press(Publisher)
Chapter 13Recombination
Abstract
As much as homologous recombination is involved in the generation of genetic diversity, eukaryotic meiosis and bacterial conjugation being the two most prominent examples, it nevertheless plays a crucial role in the maintenance of genetic stability by repairing DNA double-strand breaks (DSBs). The basic steps of recombinational DNA repair—resection, homologous DNA pairing and strand exchange, branch migration, and separation of the joined DNA molecules—are conserved in all three domains of life. Each step in every system requires the involvement of multiple enzymes, the structures of some of which have been discussed in the chapter in relation to their functions. In addition, the mechanisms of two types of Genetic Recombination—conservative site-specific recombination and transposition—that lead to DNA rearrangements have been explained based on the structures of the key enzymes.Keywords
Homologous recombination; DNA double-strand break repair; Holliday junction; Branch migration; Recombinase; Resolvase; Site-specific recombination; TranspositionExchange of genetic information between DNA molecules is continuously at work in nature. The phenomenon is known as Genetic Recombination. A very prominent way this exchange can occur is based on similarity or near-similarity of nucleotide sequences between two DNA molecules. This is called homologous recombination (HR).Examples of homologous recombination are as common as that associated with eukaryotic meiosis or observed in bacterial conjugation. The two phenomena play a crucial role in the respective organisms in the generation of genetic diversity. Homologous recombination also plays an essential role in the maintenance of genetic stability by repairing DNA double-strand breaks (DSBs).DNA damage, as we have seen in Chapter 12
- Jelena Kusic-Tisma(Author)
- 2011(Publication Date)
- IntechOpen(Publisher)
3 The Relationship Between Replication and Recombination Apolonija Bedina Zavec National Institute of Chemistry Slovenia 1. Inroduction DNA replication, the process of copying double-stranded DNA, and DNA recombination, the process of breaking DNA strand and joined to a different strand, are central characteristics of life. The aim of this chapter is to discuss the relationship between replication and recombination. Understanding the intimate links between these processes gives us a more holistic approach to understanding the functioning of a cell. Replication and recombination machineries cooperate to maintain biological inheritance and genomic integrity. While replication enables the formation of two identical DNA molecules from a single double-stranded DNA, recombination enables accurate repair of errors that occur on both strands of DNA as well as the formation of new combinations of genes. Recombination can occur between similar molecules of DNA (homologous recombination), or dissimilar molecules (non-homologous end joining). Homologous recombination predominantly occurs during and shortly after DNA replication (late S and G2), while non-homologous end joining is predominant in the G1 and early S phase of the cell cycle. What is the relationship between DNA replication and recombination processes? Mutations in some genes with a role in DNA replication cause hyper-recombination phenotypes. These mutations require recombination protein Rad52 for their viability, suggesting that the replication errors caused by mutations are repaired by recombination mechanisms (Merrill & Holm, 1998). Furthermore, many recombination genes have S phase defects when deleted. Obviously, replication and recombination processes are tightly intertwined.
- Anna K Naumova, Teruko Taketo(Authors)
- 2016(Publication Date)
- WSPC(Publisher)
Meiotic Recombination in the Human Germ Line 3 Fatima Smagulova Irset Inserm, U1085, 9 Avenue du Professeur Leon Bernard, 35000, Rennes, France Homologous recombination (HR) is the exchange of genetic information between similar deoxyribonucleic acid (DNA) molecules. In mammalian meiosis, HR is essential for correct chromosome segregation during gamete formation. Errors of HR lead to aneuploidy, formation of gametes with incorrect number of chromosomes and genetic disorders. Understanding the mechanisms of recombination is important for identifying disease-associated genomic regions and for the study of human genome evolution. With the development of new whole-genome technologies, knowledge of meiotic recombination in germ cells have advanced significantly. The recent discovery of the role of the PR domain containing 9 (PRDM9) protein in the recombination process opens new perspectives in HR research. In this review, I describe the basics of HR; introduce the pedigree, sperm typing and chromatin immunoprecipitation Sequencing (ChIP-seq) approaches that are currently used to study recombination in human germ cells and summarize the properties of recombination “hotspots”, discovered as a result of the understanding of the process involved in double-strand break (DSB) formation. Finally, I discuss the implications of the recombination events for genetic disorders in humans. 3.1 Basics Homologous recombination (HR) is a process, which normally occurs during cell division in eukaryotes. During mitosis, HR is involved in repair of deoxyribonucleic acid (DNA) double-strand breaks (DSB) caused by radiation or DNA-damaging chemicals (reviewed in (Moynahan and Jasin 2010)), it also plays a role in repair of replication fork stalling, the transient pausing of the replication (Nagaraju and Scully 2007, Hastings et al. 2009, Ciccia and Elledge 2010). In germ cells, HR is required for the correct formation of haploid gametes
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