Category: Uncategorized

FRAGMENT FROM NATURE continues from last weekend on the theme of genotype to phenotype conversion, or from DNA to observable traits. We have been immersed in the all-powerful theory of genes and destiny, but the truth is rather different. The radical conclusions we are arriving at today were completely unpredictable only 50 years ago. The phenotype is crafted from a combination of genes and the environment, often across diverse species, finding similar solutions in unrelated creatures. View in LinkedIn

RADICAL THINKING. "A major discovery of the past 20 years is that variation at certain genetic loci produce comparable phenotypic variation not only in various individuals of one population, but also in extremely diverse taxa." Contemplate this apparent radical heresy before moving on. https://lnkd.in/d3vzXnd View in LinkedIn

DECEPTIVELY SIMPLE. "Three characteristics contribute to the rapid evolution of these viruses: large populations, short generation times and high mutation rates. Every mutation, which enables its carrier to evade the host’s immune system, will be (positively) selected, passed on to the next generation and distributed more widely. Influenza viruses evolve 1 million times faster than mammals. Five years of virus evolution roughly correspond to the time span, which separates humans and chimpanzees from their last common ancestor." https://lnkd.in/d8xM5QF View in LinkedIn

CONTEXTUAL EFFECTS. "Gene-by-Environment (GxE) interaction occurs when the phenotypic effect of a given genetic change depends on environmental parameters. Similarly, epistasis, or GxG interaction, occurs when the phenotypic effect of a given genetic change depends on the allelic state of at least one other locus." https://lnkd.in/d3vzXnd View in LinkedIn

STREAMLINING AND OUTSOURCING. Extreme genome reduction in symbiotic bacteria. "These symbionts have numerous features in common, such as extraordinarily fast protein evolution and a high abundance of chaperones. Together, these features point to highly degenerate genomes that retain only the most essential functions, often including a considerable fraction of genes that serve the hosts." https://lnkd.in/dx2k-vt View in LinkedIn

REDUCTIONISM LIMITATIONS. "In summary, the classical genetic reductionist approach is inherently unable to elucidate all the factors responsible for observable characteristics in the living world but is a powerful and relevant method for dissecting the genetic levers of heritable phenotypic variation." https://lnkd.in/d3vzXnd View in LinkedIn

INCREASING COMPLEXITY. "The history of life is punctuated by evolutionary transitions which engender emergence of new levels of biological organization that involves selection acting at increasingly complex ensembles of biological entities." https://lnkd.in/d_h9CX2 View in LinkedIn

BIOLOGICAL RELATIVITY. "Misconceptions arise because phenotypes are usually defined relative to possibilities that are not formulated explicitly. Our minds and our language often tend to confuse the objects whose variation is under consideration with the variation itself, and it is essential to remind that, in genetics, the objects of interest (e.g., a given genotype, an allele or a phenotype) deserve to be defined relatively to another reference state." https://lnkd.in/d3vzXnd View in LinkedIn

THE RED HERRING. "For long some geneticists may have thought that they were dissecting the morphogenetic mechanisms underlying the formation of phenotypic traits, while their experimental approach were in fact uncovering genes whose absence or alteration (mutations, deletions, duplications, rearrangements, etc.) leads to phenotypic differences." https://lnkd.in/d3vzXnd View in LinkedIn

SLEIGHT OF HAND. "Alfred Sturtevant formulated the question of the GP map in simple terms: “one of the central problems of biology is that of differentiation – how does an egg develop into a complex many-celled organism? That is, of course, the traditional major problem of embryology; but it also appears in genetics in the form of the question, How do genes produce their effects?” (GP = genotype-phenotype relationship). https://lnkd.in/d3vzXnd View in LinkedIn