What is the quasispecies concept?

What is the quasispecies concept?

The term quasispecies describes a type of population structure in which collections of closely related genomes are subjected to a continuous process of genetic variation, competition, and selection. Usually, the distribution of mutants or variants is centered on one or several master sequences.

Why are quasispecies important in virology?

The quasispecies model is most applicable when the genome size is limited and the mutation rate is high, and so is most relevant to RNA viruses (including important pathogens) because they have high mutation rates (approx one error per round of replication), though the concepts can apply to other biological entities …

Can DNA viruses be quasispecies?

Viral quasispecies are the mutant distributions (also termed mutant swarms or mutant clouds) that are generated upon replication of RNA viruses, and some DNA viruses in infected cells and organisms.

Is SARS CoV 2 a quasispecies?

Quasispecies in RNA viruses have previously been reported for SARS-CoV and MERS-CoV [10,11], as well as within individuals during SARS-CoV-2 infection [3,12]. The present study, allowing the analysis of SARS-CoV-2 minority variants at 1%, supports the previous finding.

Why virus is called quasi living?

The RNA molecule can shed fragments of itself, and these incomplete bits can approximate some kinds of life functions. But crucially, quasi-life forms are able to replicate themselves by pirating the machinery of living cells. Since they cannot survive independently, they are technically non-life structures. Virus.

What requires a helper virus?

A helper virus is a virus that allows an otherwise-deficient coinfecting virus to replicate. These can be naturally occurring as with Hepatitis D virus, which requires Hepatitis B virus to coinfect cells in order to replicate.

What are the implications of quasispecies for antiviral therapy?

Quasispecies theory predicts that a replicating viral population will contain a large number of unique mutants, so there is a probability that an active viral infection will already have resistant mutants upon time of RNAi treatment, which could rapidly become the dominant mutation when placed under selection.

What is a viral population?

Viral quasispecies refers to a population structure that consists of extremely large numbers of variant genomes, termed mutant spectra, mutant swarms or mutant clouds. Fueled by high mutation rates, mutants arise continually, and they change in relative frequency as viral replication proceeds.

What is quasi living?

Since they cannot survive independently, they are technically non-life structures. Virus. The most familiar quasi-life form is the RNA fragment called a virus.

What is a wild type virus?

The naturally occurring, non-mutated strain of a virus. When exposed to antiretroviral (ARV) drugs, wild-type HIV can develop mutations that make the virus resistant to specific HIV drugs.

How does a helper virus work?

What is a name given to a disease causing agent composed only of protein?

Prions, so-called because they are proteinaceous, are infectious particles, smaller than viruses, that contain no nucleic acids (neither DNA nor RNA).

What is the purpose of the quasispecies theory?

Quasispecies theory is a mathematical framework that was initially formulated to explain the evolution of life in the “precellular RNA world [11] .” It builds on classical population genetics, but seeks to explore the consequences of error-prone replication and near-infinite population sizes for genome evolution [12], [13].

When did Manfred Eigen invent the quasispecies theory?

Quasispecies theory was developed in the 1970s by Manfred Eigen and Peter Schuster to explain self-organization and adaptability of primitive replicons (a term used to refer to any replicating entity), as an ingredient of hypercyclic organizations that link genotypic and phenotypic information, as an essential step in the origin of life.

How are quasispecies related to the fitness peak?

The theory predicts that a viral quasispecies at a low but evolutionarily neutral and highly connected (that is, flat) region in the fitness landscape will outcompete a quasispecies located at a higher but narrower fitness peak in which the surrounding mutants are unfit. This phenomenon has been called ‘the quasispecies effect’…

How are quasispecies related to the population structure of viruses?

A viral quasispecies is a population structure of viruses with a large numbers of variant genomes (related by mutations). Quasispecies result from high mutation rates as mutants arise continually and change in relative frequency as viral replication and selection proceeds.