linkstream2 microblog

galapagos in a carton – dobzhansky

https://books.google.com/books?id=XvAsDAAAQBAJ&pg=PA106&lpg=PA106&dq=galapagos+in+a+carton+dobzhansky&source=bl&ots=dKvEul0Vav&sig=VgM2J3sl1ST8SSOEyI8dUgj3thM&hl=en&sa=X&ved=0ahUKEwiX56WdjZHNAhVCGz4KHVVvAyUQ6AEIHDAA#v=onepage&q=galapagos%20in%20a%20carton%20dobzhansky&f=false

genetics & history

https://en.wikipedia.org/wiki/Grigori_Rasputin

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Fisher gained a scholarship to study Mathematics at the University of Cambridge in 1909, gaining a First in Astronomy in 1912.[7] In 1915 he published a paper The evolution of sexual preference[8] on sexual selection and mate choice. He published The Correlation Between Relatives on the Supposition of Mendelian Inheritance in 1918, in which he introduced the term variance and proposed its formal analysis.[9] He put forward a genetics conceptual model showing that continuous variation amongst phenotypic traits measured by the biostatisticians could be produced by the combined action of many discrete genes and thus be the result of Mendelian inheritance. This was the first step towards the establishment ofpopulation genetics and quantitative genetics, which demonstrated that natural selection could change allele frequencies in a population, resulting in reconciling its discontinuous nature with gradual evolution.[10] Joan Box, Fisher’s biographer and daughter says that Fisher had resolved this problem in 1911.[11]

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https://en.wikipedia.org/wiki/Ronald_Fisher

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The significance of chromosomal inversions for investigating genetic and evolutionary questions can be traced to Sturtevant’s (1913) publication of the first chromosome map, which included six genes present on the X chromosome of D. melanogaster (Crow 1988). Sturtevant hypothesized that the recombination frequency between linked genes was directly related to their linear distance along the chromosomes, a proposal that initiated the fertile field of gene mapping. It would later be established that there is a linear correspondence between the sequence of genes in the genetic maps and the dark and light bands in the polytene chromosomes of the salivary glands. In 1926, Sturtevant (1926) showed that the so-called C factors, which had the property of suppressing crossing over, were associated with inversions in the gene sequence, which was later confirmed in giant salivary gland
chromosomes. Sturtevant and Dobzhansky(1936) later discovered that chromosome inversions were often present as polymorphisms in several natural populations of different species of Drosophila.

Chromosome inversions frequently overlap along a chromosome, an observation exploited by Dobzhanskyand Epling (1944) to infer the succession in which the inversions have arisen one from another, although not their temporal direction; i.e., whether a chromosome band arrangement was ancestral or descendant could not be determined (the method was first introduced and applied by Sturtevant and
Dobzhansky1936). Although the direction of a particular change could not be determined, this was often apparent from the entire set. Dobzhansky would for many years exploit this discovery for
reconstructing phylogenetic “trees” reflecting ancestor-descendant relationships between chromosome arrangements within and between species. This genetic method for reconstructing evolutionary biology would later be extended byFitch and Margoliash (1967) for determining the phylogeny of protein sequences from different species and, thereby, the phylogeny of the species. Protein and DNA sequences would eventually be used to reconstruct the evolutionary history of populations from the same species, a new subdiscipline called phylogeography. This has become a burgeoning field of evolutionary research (Avise 2000). The chromosome trees constructed by Dobzhansky and collaborators over many years may be seen as early examples of species phylogenies as well as of phylogeography, since chromosome polymorphisms were often associated with distinct geographic localities.

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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1451177/

Nice discussion of “cardboard box” experiment for two fly populations

https://en.wikipedia.org/wiki/Theodosius_Dobzhansky

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Sturtevant’s most notable discoveries include the principle of genetic mapping, the first reparable gene defect, the principle of underlying fate mapping, the phenomena of unequal crossing-over, and position effect. His main contributions to science include his analysis of genetic “linkage groups,” which became classical method of chromosome mapping that we still use today.
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https://en.wikipedia.org/wiki/Alfred_Sturtevant

Discovery of X-ray mutagenesis

https://en.wikipedia.org/wiki/Hermann_Joseph_Muller

https://en.wikipedia.org/wiki/Chromosomal_crossover

https://en.wikipedia.org/wiki/Genetic_linkage

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Griffith’s experiment, reported in 1928 by Frederick Griffith,[1] was the first experiment suggesting that bacteria are capable of transferring genetic information through a process known as
transformation.[2][3] Griffith’s findings were followed by research in the late 1930s and early 40s that isolated DNA as the material that communicated this genetic information.

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transformation

https://en.wikipedia.org/wiki/Griffith%27s_experiment