What is bacterial phase variation?
In biology, phase variation is a method for dealing with rapidly varying environments without requiring random mutation. It involves the variation of protein expression, frequently in an on-off fashion, within different parts of a bacterial population.
What type of variation is phase variation?
Phase variation in general refers to a reversible switch between an “all-or-none” (on/off) expressing phase, resulting in variation in the level of expression of one or more proteins between individual cells of a clonal population.
What is the difference between phase variation and antigenic variation?
Phase variation or phenotypic switch allows the expression of a given phenotype to be switched ON or OFF. Antigenic variation refers to the expression of a number of alternative forms of an antigen on the cell surface, and at a molecular level, shares common features with phase variation mechanisms.
What is recombination phase?
Recombination Occurs During the Prolonged Prophase of Meiosis I. Figure 5. Prophase I is the longest and arguably most important segment of meiosis, because recombination occurs during this interval.
What is the purpose of antigenic variation?
Antigenic variation not only enables the pathogen to avoid the immune response in its current host, but also allows re-infection of previously infected hosts. Immunity to re-infection is based on recognition of the antigens carried by the pathogen, which are “remembered” by the acquired immune response.
What is meant by antigenic variation?
Antigenic variation refers to the observation that different isolates of a single virus species may show variable cross-reactivity when tested with a standard serum.
What is antigenic phase variation?
Antigenic variation or antigenic alteration refers to the mechanism by which an infectious agent such as a protozoan, bacterium or virus alters the proteins or carbohydrates on its surface and thus avoids a host immune response, making it one of the mechanisms of antigenic escape. It is related to phase variation.
What is an example of antigenic variation?
Examples of random antigenic variation are those that occur in viruses such as the influenza virus and the human immunodeficiency virus (HIV), which causes acquired immunodeficiency syndrome (AIDS). The major antigenic components of these viruses are glycoproteins that make up their viral coat.
What is the difference between crossing over and recombination?
The main difference between recombination and crossing over is that recombination is the production of different combinations of alleles in the offspring whereas crossing over is the exchange of genetic material between non-sister chromatids, the event which produces recombination.
What are the two causes of recombination?
Most recombination occurs naturally and can be classified into two types: (1) interchromosomal recombination, occurring through independent assortment of alleles whose loci are on different but homologous chromosomes (random orientation of pairs of homologous chromosomes in meiosis I); & (2) intrachromosomal …
Which bacterial component has most antigenic variation?
Antigenic variation in bacteria is best demonstrated by species of the genus Neisseria (most notably, Neisseria meningitidis and Neisseria gonorrhoeae, the gonococcus); species of the genus Streptococcus and the Mycoplasma.
What causes antigenic variation?
Antigenic variation in microbes is created via two general types of mechanisms, genetic and epigenetic. Genetic events (mutation and recombination) change the DNA sequence of an antigen encoding gene or its regulatory elements, thereby altering either the level of expression or the amino acid sequence of its product.
What is antigenic variation in microbiology?
Antigenic variation refers to the expression of functionally conserved moieties within a clonal population that are antigenically distinct. The genetic information for producing a family of antigenic variants is available in the cell, but only one variant is expressed at a given time.
What are the three types of genetic recombination?
The three types of genetic recombination in bacteria are transformation, transduction and conjugation.
What are the 3 methods of genetic recombination?
What is the difference between recombination and crossing over?
What are the 3 methods of genetic transfer in bacteria?
There are three “classical” methods of DNA transfer in nature: bacterial conjugation, natural transformation, and transduction (von Wintersdorff et al., 2016). Via HGT, exogenous DNA can be transferred from one bacterium to another even if they are only distantly related (Chen et al., 2005; Burton and Dubnau, 2010).
What are 3 ways that bacteria share genes?
There are three mechanisms of horizontal gene transfer in bacteria: transformation, transduction, and conjugation.
How do bacteria gain genetic variation?
However, bacteria have found ways to increase their genetic diversity through three recombination techniques: transduction, transformation and conjugation.
What causes genetic variation in bacteria?
Prokaryotic cells have developed a number of methods for recombining their genetic material, which, in turn, contributes to their genetic diversity. The three most common ways that bacteria diversify their DNA are transformation, conjugation, and transduction.
What are the 3 ways bacteria gain antibiotic resistance?
The three fundamental mechanisms of antimicrobial resistance are (1) enzymatic degradation of antibacterial drugs, (2) alteration of bacterial proteins that are antimicrobial targets, and (3) changes in membrane permeability to antibiotics.
What two ways do bacteria transfer genes to other bacteria?
Ways for bacteria to share their genes:
Conjugation: Two bacteria can pair up and connect through structures in the cell membranes and then transfer DNA from one bacterial cell to another. Transduction: There are viruses called bacteriophages that can infect bacteria.
What causes variation in bacteria?
Any change in the genotype of a bacterium or its phenotype is known as variation. Genotypic variation can occur as a result of changes in the genes by way of mutation, loss or acquisition of new genetic elements. These variations are heritable.
Why genetic variation is important in bacteria?
Genetic diversity is important because it gives species a better chance of survival. However, genetic diversity can be lost when populations get smaller and isolated, which decreases a species’ ability to adapt and survive.
What are the types of genetic variation?
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- Missense variant. Credit: U.S. National Library of Medicine.
- Nonsense variant. Credit: U.S. National Library of Medicine.
- Insertion variant. Credit: U.S. National Library of Medicine.
- Deletion variant.
- Duplication.
- Amino acids.
- Frameshift variant.
- Repeat expansion variant.