If a mutation is found in about 50% of offspring’s DNA, it is likely to be a germline mutation passed on through either the mother’s egg or the father’s sperm, the researchers concluded. attached. Natural selection can act directly on such mutations. Low-frequency mutations were thought to have occurred spontaneously in extragermline tissues. Because they are not inherited, they are less relevant to evolution.
(Surprisingly, the family trio’s disagreement informed researchers that the father listed by the zoo had nothing to do with the baby. Zoo representatives shrugged upon hearing the news. , I used to say that there might have been two males in the cage, the other being the winner,” joked Bergeron.)
Ultimately, the researchers created a usable trio of 151 representatives of physically, metabolically, and behaviorally diverse species, including giant killer whales, small Siamese fighting fish, Texas geckos, and humans. They then compared the species’ mutation rate to what we know about its behavior and traits, called its life history. They also considered a variety of statistical measures called effective population size, which roughly corresponds to the number of individuals required to represent genetic diversity. (For example, the human population today is her 8 billion, but scientists usually estimate the effective population size to be about her 10,000 or less.) Bergeron and her colleagues I looked for patterns in number relationships.
The most surprising finding revealed by the data was the wide range of germline mutation rates. When the researchers measured how often mutations occurred from generation to generation, the differences between species were only about 40-fold, and when compared to differences in body size, lifespan and other traits, the differences were much higher. looks pretty small, Bergeron said. However, when looking at mutation rates by year rather than by generation, the range increased about 120-fold, larger than previous studies had suggested.
source of change
The study authors found that the larger the average effective population size of a species, the lower its mutation rate. It was a good proof of “”.drift barrier hypothesisIt was invented by Lynch about ten years ago. “Since most mutations are deleterious, selection is relentless in trying to reduce mutation rates,” Lynch explained. However, in species with a small effective population size, genetic drift (the effect of pure chance on the spread of mutations) is stronger, thus weakening natural selection. This increases the mutation rate.
The findings also support another idea in the scientific literature. Male-led evolutionary hypothesisThis suggests that males may contribute more mutations to the evolution of some species than females. Bergeron and colleagues found that, in at least mammals and birds, but not reptiles or fish, males tended to have higher rates of germ-line mutations than females.
The authors focused on possible reasons for these differences. Males of any species are constantly copying DNA to make sperm, so they face limitless opportunities for mutation. Female fish and reptiles also lay eggs throughout their lives and are at risk for similar genetic errors. However, female mammals and birds are essentially born with all the egg cells they will produce, so their germline is more protected.
