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This week on SciShow News, we explore how our genes change with the seasons! Plus, it turns out that even flies get scared sometimes.

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It’ll soon be summer here in the northern hemisphere, and winter for those of you on the other half of the planet.   Of course, plenty of things change with the seasons: the weather, the number of daylight hours, whether or not you have school...   And according to new research, there are other things that change, as well- like your genes.   For a long time, doctors, patients, and researchers have noticed that some diseases, like heart disease, type 1 diabetes, and rheumatoid arthritis seem to get worse during the winter. But they weren’t sure why.   Now, it looks like there’s a very good reason: genes associated with your immune system seem to change expression -- that is, basically, to turn off and on -- based on the season.   Researchers from the UK and Germany studied the genomes of more than 16,000 people from all over the world, using blood and fat samples that had been collected at different times of year.    Since your genes code for particular proteins, if a sample had more of a certain kind of protein at a specific time of year, that meant the gene associated with it was more active.   And the patterns that showed up in the subjects showed some clear similarities.   Out of nearly 23,000 genes, over 5,000 were more active certain times of year.   And the patterns were actually reversed in people who lived in different hemispheres.    So genes that were more active in a German during December were also more likely to be active in an Australian in June.    One immune system gene, called ARNTL, is known to suppress inflammation in mice, and it turned out to be more active in people during the summer.   This could explain why some autoimmune diseases, like rheumatoid arthritis, tend to flare up in winter -- because that’s when the genes that help reduce inflammation aren’t expressed as strongly.   Similarly, genes that code for the antibodies that fight diseases like yellow fever, influenza, and meningitis were found to be more active during the winter.   Now that makes some sense, because winter is flu season, but it also means that winter may be most effective time to vaccinate against these diseases, so vaccines can evoke the best possible response from your immune system.    As for the gene that showed the strongest seasonal preference -- geneticists know which protein it codes for, but they have no idea what it does.    So, yeah, we have a lot more to learn, but the results suggest that our bodies may be more in tune with our yearly trek around the sun than we’d thought.   Speaking of genetics, another team of scientists has been investigating an animal that’s taught us a whole lot about the field: the famous fruit fly.    And it seems that they experience fear?   It’s kind of tough to identify emotions in animals like flies, because ... how would you know fly-fear if you saw it?   But a group of American researchers has translated fear into a few basic behaviors, so that animals’ responses could be studied without assigning them subjective human feelings, like dread or anxiety.   The scientists arrived at behaviors like whether an animal’s response was persistent, meaning that it lasted for a while, or if it was scalable, in which case, repeated stimuli would cause a greater response.   They called these traits emotion primitives -- sort of like the primal components of emotions that some animals may have in common.   To test for those components, the team put groups of fruit flies into well-lit containers, and then passed an object over them to cast a shadow, just like a bird or a rodent would if it were approaching to prey on them.   Then, they observed the flies’ responses.   Sometimes, the flies just froze -- a defensive reflex, which makes a lot of sense.   But other times, the flies started hopping around erratically when the shadows passed over them -- and the more the shadow returned, the more agitated they seemed to become.   The researchers then tried the experiment on flies as they were feeding. And they found that flies not only abandoned their food when the shadow approached, but the more often the shadow came by, the longer they took to return to their food.    So, the flies responded to these repeated threats, in ways that were both persistent and scalable, which -- to the researchers, at least -- is a lot like what we call fear.   But other than making everyone feel bad for a bunch of fruit flies, what does this accomplish?   Well, the researchers want to study the biological, and evolutionary, origins of fear. And since fruit flies and humans have about 60 percent of their genomes in common, studies like this can be useful in researching, and eventually treating, prolonged states of anxiety, fear, and other emotional disorders in people.   So, while you’re making out your thank you cards for the poor fruit flies, allow me to thank you for watching SciShow News, which is brought to you by our patrons on Patreon. If you want to help us keep making this show, you can go to And don’t forget to go to and subscribe!