Halloween is this weekend. We’re putting finishing touches on costumes, prepping our candy supply, and sharing the science behind some of this holiday’s most iconic symbols.
Monster Pumpkins: Regardless of what your pumpkin weighs, genetically it’s a giant. Pumpkins have 20 chromosomes and an average genome size of 1.09 pg. By comparison, closely related cucumbers and watermelons have 7 and 11 chromosomes. A 2017 genomic study revealed a host of duplicate genes which suggests that two separate pumpkin genomes combined into a single mega one long ago. Such merging occasionally happens in plants and results in polyploidy – the condition of having multiple chromosome sets within a single cell. But pumpkins are unusual even among polyploids. Evidence in their genome suggests that merging happened not once but twice, making the plant a paleotetraploid (or “old four sets”). In addition, the duplicate DNAs seem to peacefully coexist whereas in many plants gene copies are whittled down over time. For more about the pumpkin genome check out this article.
Ghost Populations: The term “Ghost Population” might conjure up the place where Casper the friendly ghost eventually finds a happy ever after. Instead, it’s an important concept in population genetics. Sometimes when scientists examine many genomes from within a species they find evidence of an unknown ancient lineage for which there is no fossil record or current genetic samples. This lineage, indicated by statistics alone, is known as a “ghost population.” This happened in 2012 when a study into ancient human migration routes found genetic evidence of a group of humans living in Siberia who later expanded across America. A year later fossil remains from this ghost population were discovered! Check out this great Nature news article on human ghost populations.
Synthetic Spider Web: Scientists have found a way to produce large amounts of this spooky, silky, and strong substance by using the bacteria Rhodovulum sulfidophilum as biofactories. To do this they introduce a plasmid carrying the spider gene MaSp1 into R. sulfidophilum and grow the resulting recombinant bacteria. These growing bacteria produce the MaSp1 protein which is then harvested and isolated. Using R. sulfidophilum as a silk biofactory was key to the success of this project as these organisms require only sunlight, carbon dioxide, and nitrogen to thrive and grow best in easy-to-maintain saltwater. Not to mention it’s a beautiful purple color! Altogether the process seems preferable to the idea of farming spiders. The latter we’ll leave to the next horror movie. Read more about this research project here. Read more about the discovery here.
Halloween Genes: In the late 1980s geneticists studying fruit flies identified a group of lethal mutations that disrupted embryonic development. More specifically, larvae with the mutations had trouble properly forming cuticle in their exoskeleton. Studying these mutations involved some fairly creepy observational data including grouping larvae into “normal”, “no differentiation between the cuticle and head skeleton”, “only head skeleton visible”, and “mouthparts poorly differentiated”. These conditions were eventually linked to specific genes and given awesome names such as the disembodied gene (no head), the haunted gene (only head), and the mummy gene (poorly formed mouth). Further research showed that the Halloween genes code for an enzyme that helps in the synthetases of a hormone essential for molting. Read all about the disembodied gene here.
Looking for a way to bring a little of Halloween into your biotech classroom? Assign one of these articles as extra credit reading over the weekend. Or check out this post which highlights three great Halloween-themed experiments.