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The crisis hidden in genes: How disease-causing mutations quietly change our genomes?
Deep within biology, invisible threats lurk in the genome. These threats may exist in the form of pathogenic mutations, causing potential crises for species and their survival. As genome research deepens, scientists are becoming increasingly aware of how these mutations quietly accumulate in a population and affect overall adaptability.
Genetic load not only affects the reproductive ability of individuals, but also creates greater risks at the population level, and even triggers the risk of extinction.
The concept of genetic load refers to the difference between the fitness of the average genotype in a population and a reference genotype (usually an ideal state). This difference helps explain why some species are so defenseless in the face of environmental change. According to relevant research, groups with high genetic load tend to produce fewer surviving offspring than groups with low genetic load under the same environmental conditions. This situation indicates that species face the risk of extinction as they gradually accumulate harmful mutations.
One of the major contributors to genetic burden is deleterious mutations. According to the Herdan-Mueller theorem, there is a certain relationship between the harmful mutation rate and gene load. This means that even if some mutations have a small impact on fitness, if these mutations are present in large numbers in the gene pool, they will cause an overall decrease in fitness. This is especially true in asexually reproducing organisms, which face the "Muller clamp" effect, a phenomenon in which the loss of the optimal genotype prevents the return of the optimal state through genetic recombination.
Two types of deleterious mutations, including unfavorable mutations and beneficial mutations, both may cause the genetic load to become saturated or increase dramatically.
In addition to harmful mutations, genetic load is closely related to how a species reproduces. Taking humans as an example, the increased homogeneity caused by inbreeding will lead to offspring carrying a higher proportion of recessive pathogenic variants. This is the so-called inbreeding suppression effect. In addition, in small-scale groups, if endogamy is carried out for a long time, disease-causing genes may flood the entire gene pool, increasing the risk of extinction.
However, even under the influence of genetic load, emerging beneficial mutations can create variations that are superior to existing genotypes. Among them, they include substitution burden and lag burden. The latter refers to the gap between the theoretically optimal genotype and the population average genotype. This process not only involves the survival of organisms, but also profoundly affects the rate of evolution of organisms.
Optimizing the genotype acquisition process is crucial because it is one of the factors that affects fitness.
Another dynamic factor in genetic burden is genetic recombination and segregation burden. These phenomena often cause alleles belonging to different genotypes to lose their optimal coordination during recombination, resulting in reduced fitness of offspring. Especially when there is an imbalance of superior genetic links, recombination and genetic partitioning will further increase the burden on genes.
Additionally, genetic load may be further complicated by the introduction of alien species. When unadapted alien species enter a new environment, although they may introduce some beneficial genes, they may also disrupt the local gene pool and increase the burden of adaptation. This process of overturning the original genetic structure may have long-term effects on native species and even lead to significant changes in ecosystems.
When genetic load reaches a critical point, whether through natural selection or the accumulation of mutations, the consequences can have irreversible effects on the entire ecosystem.
The accumulation of genetic load has attracted the attention of many scientists, from early Hermann Joseph Muller to today's genetics researchers, who are concerned about disease-causing mutations in the human genome. These studies not only help us understand how genes affect the adaptability of organisms, but also remind us that the life of every species may be unknowingly threatened. As genomics continues to advance, we need to think about how to better manage these crises hidden in genes to protect species in the future?
