Yeast cells: 20th and 21st Century Views
November 15, 2013 | James Kohl
Description: James A. Shapiro’s Evolution: A View from the 21st Century proposes an important new paradigm for understanding biological evolution. Shapiro demonstrates why traditional views of evolution are inadequate to explain the latest evidence, and presents a compelling alternative. His information- and systems-based approach integrates advances in symbiogenesis, epigenetics, and mobile genetic elements, and points toward an emerging synthesis of physical, information, and biological sciences.
You may be able to use the “Look Inside” feature at Amazon.com to find: “Signaling from the cell surface to the genome: Pheromone response in the sexually aroused yeast cell (Page 21).”
“Yeast” is mentioned 46 times in various contexts that help to stress the importance of this model organism (as we did in 1996 in the context of sex differences at the advent of sexual reproduction in a unicellular organism).
From Fertilization to Adult Sexual Behavior: Abstract excerpt: All these factors affect the internal workings of the individual and intervene in structuring how the social environment might or might not modify sexual behavior.
Our view from the 20th century: Molecular epigenetics
“Yet another kind of epigenetic imprinting occurs in species as diverse as yeast, Drosophila, mice, and humans and is based upon small DNA-binding proteins called “chromo domain” proteins, e.g., polycomb. These proteins affect chromatin structure, often in telomeric regions, and thereby affect transcription and silencing of various genes…. Small intranuclear proteins also participate in generating alternative splicing techniques of pre-mRNA and, by this mechanism, contribute to sexual differentiation in at least two species, Drosophila melanogaster and Caenorhabditis elegans… That similar proteins perform functions in humans suggests the possibility that some human sex differences may arise from alternative splicings of otherwise identical genes.”
“Parenthetically it is interesting to note even the yeast Saccharomyces cerevisiae has a gene-based equivalent of sexual orientation (i.e., a-factor and alpha-factor physiologies). These differences arise from different epigenetic modifications of an otherwise identical MAT locus.”
Excerpted from “Nothing in Biology Makes Any Sense Except in the Light of Evolution” (link opens the free .pdf)
“…the so called alpha chains of hemoglobin have identical sequences of amino acids in man and the chimpanzee, but they differ in a single amino acid (out of 141) in the gorilla.”
“…and animals differ from yeasts and molds in 56 to 72 amino acids.”
Since 1973, all experimental evidence has shown that a single amino acid substitution can cause phenotypic changes that differentiate species and that species-specific pheromones control the physiology of reproduction. Thus, what DNA teaches us about evolution is that the epigenetic landscape becomes the physical landscape of DNA and phenotype via nutrient-dependent pheromone-controlled alternative splicings and changes in amino acids. What is missing from most current representations of biologically based adaptations is the fact that they are not due to uncontrolled random mutations and natural selection for something associated with the random mutations. From any biological perspective, mutation-initiated natural selection does not make sense. Obviously, Dobzhansky recognized that fact 40 years ago. Why don’t evolutionary theorists recognize that fact today?
Video: What DNA Teaches About Evolution — presentation by Dr. James A. Shapiro in the 2012-2013 Linus Pauling Memorial Lectures Published on 23 Oct 2013