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Category Archive for 'Genetics'

After posting my last commentary on the ongoing Ebola outbreak in West Africa, I listened to the netcast, This Week in Virology (www.twiv.tv), for September 14, 2014.  TWiV sessions, hosted by Vincent Racaniello, a well-known virologist at Columbia University, are generally highly informative, typically offering thoughtful discussions about recently published studies pertaining to viruses or […]

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Over the past several weeks the health news has been dominated by the outbreak of infections by Ebola virus (EBOV) in several West African nations: Guinea, Sierra Leone, Liberia, and Nigeria.  A study (Gire et al., 2014) published online at the end of August and now in print by a large collaborative group based in […]

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Altshuler and colleagues (Nature Genetics, 2014) recently reported a study of about 150,000 individuals representing five different ancestral groups in which they identified twelve low-frequency variants of the gene SLC30A8 through either genomic sequencing or genotyping.  These variants are all predicted to truncate the gene product (ZnT8), a protein involved in zinc transport in beta […]

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Epistasis refers to the influence of one genomic mutation or variant on the phenotypic effects of another mutation or variant.  Based on available evidence and theory, this phenomenon has a major influence on evolutionary trajectories for organisms of all sorts.  The role of epistasis has been studied primarily in the context of adaptive evolutionary change.  […]

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Toxoplasma gondii is an intracellular protozoan parasite that infects many different vertebrate species asexually and undergoes a sexual cycle after infecting cats (http://www.cdc.gov/parasites/toxoplasmosis/, 2013).  Parasite oocysts are potentially introduced into the human environment in cat feces.  T. gondii is of interest in clinical medicine because humans can serve as accidental intermediate hosts when they ingest […]

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A prion is a protein that can adopt a conformation other than the ‘standard’ functional conformation and this alternative conformation favors self-association. The aggregation-associated conformation can then be imposed on additional copies of the protein in the original conformation.  This self-templating mechanism for propagation is known primarily for causing neurodegenerative conditions in humans and in […]

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This past December, science writer David Dobbs published an essay (2013) in the online magazine Aeon (aeon.co/magazine/) that purports to explain why the ‘selfish gene’ concept is outmoded and should be retired.  It elicited a good deal of commentary, and in early March, Aeon published responses (Sapolsky et al., 2014) to the original article from […]

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Geneticists have recognized for some time that many genes exhibit pleiotropy, meaning that one mutation can manifest in two or more distinguishable phenotypic effects. In a fascinating study recently published in Science [2014 Jan 10;343(6167):152-7. doi:10.1126/science.1246886], Joseph et al. offer evidence for an example of pleiotropy in which the distinct phenotypic effects associated with mutation […]

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Last month, I completed teaching a graduate course for the tenth time.  After several years (in the early 1990’s) of thinking about launching a new alternate-year seminar course and then planning it, I began teaching PATH 480 in the fall of 1994.  The original name of the course, maintained through the first seven times I […]

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Biomedical scientists and biologists routinely consider how selection shapes the structure and function of proteins of interest.  Less commonly, I suspect, do we consider how selection for attributes other than protein structure and function can favor or disfavor nucleotide sequences that encode particular amino acid sequences.   A new study (Stergachis et al., 2013) published in […]

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Three new papers (Kilpinen et al., 2013; McVickers et al., 2013; Kasowski et al., 2013) published earlier this month in Science all address the effects on human patterns of gene expression and other phenotypes of 1) genetic variation in non-protein coding regions of the genome and 2) covalent modifications of chromatin, the complex of DNA […]

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In his 1987 book, “The Evolution of Individuality,” Leo Buss addressed a fundamental biological question: “How could individual multicellular animals (known as metazoans), like sea anemones, insects, frogs, and humans arise?”  Buss focused on a key challenge confronting any multicellular animal with differentiated cell types performing different functions: the potential conflict between selection on the […]

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A central focus of recent research aimed at developing a vaccine for HIV-1 is the identification of potent broadly-neutralizing antibodies (bNAbs).  Due to work from several laboratories, many such antibodies have now been identified, produced in quantity as monoclonal antibodies, and characterized with respect to key properties such as epitope specificity, affinity for the corresponding […]

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Currently, I am on vacation near the beach in South Carolina.  Consequently, I have opted for a topic that is bit different than the majority of my monthly commentaries in that it focuses not on a recent original report but instead on a conceptual point made in a book over thirty years ago.  Nevertheless, after […]

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In lay publications, it is commonplace for writers to refer to the deoxynucleotide sequence of an individual’s nuclear genome as that individual’s “code” and to the determination of that sequence as “deciphering the code.”   Molecular biologists mean by the “genetic code,” not a DNA sequence but the relationships between RNA (or DNA) nucleotide triplets and […]

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The term “genetic code” is associated with a measure of ambiguity.  For molecular biologists, “genetic code” has historically referred to a table that provides for each messenger RNA ribonucleotide triplet the corresponding amino acid that is incorporated into the growing end of a nascent polypeptide chain, i.e. the translation from RNA sequence to protein sequence.  […]

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In a previous post (http://evmedreview.com/?p=1034), I discussed a study from Stuart Orkin’s lab that illustrated the exploitation of genetic variants that influence a disease-related phenotype to design a possible therapy for a murine version of sickle cell disease.  Increased fetal hemoglobin expression had been demonstrated to diminish the severity of sickle cell disease in mice, […]

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The consortium of investigators known as ENCODE (ENCyclopedia Of DNA Elements) published, with much publicity, a series of about thirty papers last fall purporting to “identify all functional elements in the human genome sequence” (https://www.genome.gov/ENCODE/).  Dan Graur, an evolutionary geneticist at the University of Houston, and his associates have published a paper in Genome Biology […]

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In the past six months, I have encountered a review, by Thomas Nagel in The New York Review of Books (2012), of Alvin Plantinga’s latest book (Where the Conflict Really Lies: Science, Religion, and Naturalism, 2011 ) and a review, by Alvin Plantinga in The New Republic (2012), of Thomas Nagel’s latest book (Mind and Cosmos: […]

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In 1996, Dean et al. (Science), demonstrated that a loss-of-function allele (CCR5Δ32) encoding a version of the chemokine receptor, CCR5, confers very substantial resistance to infection with HIV-1 in the homozygous state and slows progression in the heterozygous state.  Given the relatively recent origin of HIV-1, this finding raised the question of what source of […]

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