Category: Uncategorized

PART B. "A complementary picture emerges with respect to time. A steady influx of mutations affects the whole reproductive span. Hazards begin to increase linearly with time at all ages. At older ages, where selective pressure is always low, this linear increase continues unabated, whereas at younger ages it is slowed for a while by outflow due to natural selection." http://www.pnas.org/content/110/25/10141.full View in LinkedIn

PARASITIC SIMPLIFICATION. "It has been well known for decades that the evolution of numerous parasitic and symbiotic organisms entails simplification rather than complexification. In particular, bacteria that evolve from free-living forms to obligate intracellular parasites can lose up to 95% of their gene repertoires without compromising the ancestral set of highly conserved genes involved in core cellular functions." http://onlinelibrary.wiley.com/doi/10.1002/bies.201300037/full View in LinkedIn

THE THEORY UNRAVELS. "However, if we try to construct an equilibrium with some specific wall of death, we find too little remaining net fertility very close to the wall to balance mutation there. Each wall of death implies an earlier one. The instability propagates down through the whole reproductive span, and our construction unravels." http://www.pnas.org/content/110/25/10141.full View in LinkedIn

THEORY CONTINUED. "At sufficiently advanced ages, remaining net fertility necessarily drops below any mutation rate that is bounded below. If the force of selection depends only on remaining net fertility, selection cannot balance mutation, and such ages must lie beyond a wall of death." http://www.pnas.org/content/110/25/10141.full View in LinkedIn

THE THEORY. "Lotka’s intrinsic rate of natural increase, with respect to an increment to age-specific mortality at an age a. Thus, he obtained a linear approximation for loss in fitness due to any deleterious mutations that raised mortality at an age a. The greater the loss in fitness, the faster should mutant alleles be selected out of a population, and the fewer should be found at equilibrium as recurring mutations balance natural selection." https://lnkd.in/eyTNv3H View in LinkedIn

MUTATION RATE. "Currently, the rate of mutation in humans is estimated to be anywhere from 70–150 mutations per generation. By this line of reasoning, we would estimate that, at most, only 1% of the nucleotides in the genome are essential for viability in a strict sequence-specific way." http://journals.plos.org/plosgenetics/article?id=10.1371/journal.pgen.1004351 View in LinkedIn

MUTATION BREAKPOINT. "This rate is approximately one deleterious mutation per generation. In this context it becomes clear that the overall mutation rate would place an upper limit to the amount of functional DNA." http://journals.plos.org/plosgenetics/article?id=10.1371/journal.pgen.1004351 View in LinkedIn

BIRTH OF NEW GENES. "Rarely, these mutations will turn out to be beneficial, and a new gene may arise (“neofunctionalization”)." http://journals.plos.org/plosgenetics/article?id=10.1371/journal.pgen.1004351 View in LinkedIn

FREE PASS. "Gene duplication can alleviate the constraint imposed by natural selection on changes to important gene regions by allowing one copy to maintain the original function as the other undergoes mutation." http://journals.plos.org/plosgenetics/article?id=10.1371/journal.pgen.1004351 View in LinkedIn

BAD GENE ACCUMULATION. "However, if the rate at which these mutations are generated is higher than the rate at which natural selection can weed them out, then the collective genomes of the organisms in the species will suffer a meltdown as the total number of deleterious alleles increases with each generation." http://journals.plos.org/plosgenetics/article?id=10.1371/journal.pgen.1004351 View in LinkedIn