Microbes are the planetary engineers of the biogeochemical cycles that sustain all life on earth. At the molecular scale, the biological turnover of such key elements as hydrogen, carbon, oxygen, nitrogen, iron and sulfur depends on the enzymatic transfer of electrons from reduced (electron-donating) to oxidized (electron-accepting) forms of these elements. On the global scale and over geological time, reduced substrates and oxidized products map to a vast, often circuitous flux between the interior depths of the mantle and the oceans, land, and atmosphere.
By John Tran, Biochemistry & Molecular Biology ’14
Have you ever wanted to learn more about the plant model organism?
Plants have many unique properties that make them especially important to all aspects of life. They provide oxygen, food, and energy, so you could imagine that there are many cellular and molecular processes that are involved in plants. For these reasons, we want to better understand plants using a model organism called Arabidopsis. Here, we talk about the properties of Arabidopsis and present an example of a genetic experiment, which could be used to improve the quality of apple trees.
One of the central pursuits of modern human genetics is to move beyond genomic correlation. That is, to demonstrate experimentally why a specific genetic variant may be associated with a disease. New work in Nature Genetics from an international team lead by Philippe Froguel at Imperial College in London does just this – demonstrating an interesting link between saliva and obesity. Basically, all humans express amylase, a salivary enzyme that breaks down complex carbohydrates into absorbable sugars. The researchers found that people with more copies of the gene had a significantly decreased risk of developing obesity. People with fewer copies expressed less amylase, and it was hypothesized that this alteration in gastrointestinal carbohydrate metabolism affected insulin signaling, blood sugar levels, as well as the microbial community in the gut. This finding has implications for the rational design of digestive enzyme-based therapies for obesity and other metabolic disorders.
Froguel, Philippe, et al. “Low copy number of the salivary amylase gene predisposes to obesity.” Nature Genetics vol. 46, p. 492-497 (2014).
Viral evolution is an emerging field in biology that has great implications for human health. T7 is a phage virus, meaning it infects bacteria, and is a powerful model system in evolutionary virology. In a recent experiment, a team of biologists sought to understand the degree to which genetic elements engineered into the T7 phage genome affected the phage’s rate of propagation. In this context, the genetic elements are sequences of DNA that are inserted between genes that allow for researchers to manipulate gene regulatory networks. This allows biologists to probe how phenotypes change when gene-gene interactions are perturbed. Previous studies had shown that such genomic elements led to decreased fitness for the virus, but these investigators hoped to better understand how exactly such a system would evolve in laboratory conditions.
To address their questions, the scientists grew both T7 viruses with and without design elements in each of two conditions. One condition was in a nutritious broth that used one intestinal bacterium as a host, and the other in a glucose sugar medium that had a different host bacterium. Both T7 strains were allowed to grow for 700-1000 generations in the glucose media and 100 generations in the broth media. Limitless bacteria were provided for the phages in order to encourage growth, and the researchers hypothesized that their experiment would allow enough time for the maladapted viruses to slough off deleterious design elements through evolutionary adaptation. Continue reading Viral Evolution→
By Marisa Sanchez, Molecular and Cellular Biology ‘15
The genomes of male and female mammals differ by one chromosome. The Y chromosome is only present in males, and is responsible for initiating the physiological and morphological differences between the sexes. This has not always been the case though; at one point, the X and Y were identical, and over time the Y chromosome began to differentiate from the X chromosome and shrink in size. The Y chromosome today only has 20 genes, whereas the X chromosome has over 1,000 genes. Continue reading Origin of the Y Chromosome→
Cheating in sports in not a new phenomenon. In the modern era, numerous athletes participate in blood doping by injecting erythropoietin (EPO) into their blood to increase the amount of red blood cells and thus improve their athletic performance. EPO is a protein hormone produced by the kidney which stimulates the production of red blood cells when released into the bloodstream. Increased red blood production increases the amount of oxygen available in the body and boosts an athlete’s performance. Yannis Pitsiladis, a psychologist in Scotland, is at the forefront of developing anti-doping testing based on the genetic fingerprint left by drugs. Conventionally researches developed tests to find the drug, but Pitsiladis has taken another approach. He is developing a new generation of tests that will gather evidence from the doper’s own body.
Most people know that poor diet, lack of exercise, and smoking as an adult can increase the risk of developing cardiovascular disease (CVD) and Type II diabetes. However, research over the past couple of decades has shown that risk for CVD and type II diabetes could begin as early as prenatally through adverse exposures, such as overnutrition and placental insufficiency. Some mechanisms involved in determining risk for CVD and Type II diabetes are oxidative stress, inflammation, lipotoxicity, and epigenetics. Continue reading Prenatal Exposures and Risk for Chronic Diseases Later in Life→
Biostatisticians led by Knut Wittkowski at Rockefeller University Hospital have employed new methods of genome-wide association studies to identify genes that they believe to be associated with autism. The researchers compared genomes of patients with varying degrees of autism to healthy patients and were able to identify genetic variations that seem to be linked to the pathology of neural development in young children. The technique used to identify these genes is unique. Rather than traditional genome association, which searches for single nucleotide polymorphisms (SNPs), this new method looks for combinations of several SNPs that are common in patients with a disease. Wittkowski also compared this new autism profile to patients with childhood epilepsy and found mutations in similar genes that control axonal guidance and calcium signaling. Both of these are important in the developing brain to ensure that the correct connections are made. Continue reading Genome-Wide Association Identifies Genes Linked to Autism→
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