Question: What is the evolutionary process described by the "Muller's ratchet" model?

Context:
Muller's ratchet is a paradigmatic model for the accumulation of deleterious mutations in a population of finite size. A click of the ratchet occurs when all individuals with the least number of deleterious mutations are lost irreversibly due to a stochastic fluctuation.
Population bottlenecks can have major effects in the evolution of RNA viruses, but their possible influence in the evolution of DNA viruses is largely unknown.
The accumulation of deleterious mutations of a population directly contributes to the fate as to how long the population would exist, a process often described as Muller's ratchet with the absorbing phenomenon.
Genetic diversity is thought to be important in allowing RNA viruses to explore sequence space, facilitating adaptation to changing environments and hosts. Some arboviruses that infect both a mosquito vector and a mammalian host are known to experience population bottlenecks in their vectors, which may constrain their genetic diversity and could potentially lead to extinction events via Muller's ratchet.
The accumulation of deleterious mutations is driven by rare fluctuations that lead to the loss of all mutation free individuals, a process known as Muller's ratchet.
The vast majority of mutations are deleterious and are eliminated by purifying selection. Yet in finite asexual populations, purifying selection cannot completely prevent the accumulation of deleterious mutations due to Muller's ratchet: once lost by stochastic drift, the most-fit class of genotypes is lost forever.
Primary bacterial endosymbionts of insects (p-endosymbionts) are thought to be undergoing the process of Muller's ratchet where they accrue slightly deleterious mutations due to genetic drift in small populations with negligible recombination rates.
Computer simulations of substitution of favorable mutants and of the long-term increase of deleterious mutants verified the essential correctness of the original Fisher-Muller argument and the reality of the Muller ratchet mechanism.
The theory of Muller' Ratchet predicts that small asexual populations are doomed to accumulate ever-increasing deleterious mutation loads as a consequence of the magnified power of genetic drift and mutation that accompanies small population size.
It also predicts the "ratchet mechanism" discovered by Muller, who pointed out that deleterious mutants would more readily increase in a population without recombination.
We also demonstrate that during repeated genetic bottleneck passages, accumulation of deleterious mutations does occur in a stepwise (ratchet-like) manner as originally proposed by Muller.
Muller proposed that an asexual organism will inevitably accumulate deleterious mutations, resulting in an increase of the mutational load and an inexorable, ratchet-like, loss of the least mutated class [Muller, H.
In asexual populations, as Muller noted, the loss is irreversible and the load of deleterious mutations increases in a ratchet-like manner with the successive loss of the least-mutated individuals.
BACKGROUND: The accumulation of deleterious mutations of a population directly contributes to the fate as to how long the population would exist, a process often described as Mullers ratchet with the absorbing phenomenon.
The accumulation of deleterious mutations is driven by rare fluctuations that lead to the loss of all mutation free individuals, a process known as Mullers ratchet.
Deleterious mutations can accumulate in asexual haploid genomes through the process known as Muller's ratchet.
Deleterious mutations can accumulate in asexual haploid genomes through the process known as Muller's ratchet
The accumulation of deleterious mutations of a population directly contributes to the fate as to how long the population would exist, a process often described as Muller's ratchet with the absorbing phenomenon

Answer: The vast majority of mutations are deleterious and are eliminated by purifying selection. Yet in finite populations, purifying selection cannot completely prevent the accumulation of deleterious mutations. Muller's ratchet is a paradigmatic model for the accumulation of deleterious mutations in a population of finite size, due to genetic drift. Muller's ratchet suggests that population bottlenecks, which may constrain the genetic diversity of a population, could lead to extinction of all individuals with the least number of deleterious mutations, due to a stochastic fluctuation. When the most-fit class of genotypes is lost, it is lost irreversibly.