AP Biology class blog for discussing current research in Biology

Author: mosmosisjones

Should We Use It: Crispr-Cas 9 Edition


Arguably the greatest thing to happen to genetics since the Human Genome Project, Crispr-Cas 9 has been getting a lot of attention.  The Los Angeles Times wrote an article approximately 4 months ago discussing the ins and outs of the new gene editing breakthrough.  The concept of editing genes is nothing new for scientists.  They’ve been doing it since the 1970s.  So many people are asking “What makes Crispr so special?”  The answer is convenience.  Crispr-Cas 9, although still filled with flaws, is the easiest gene editing tool to use out there right now.  Scientists from UC Irvine and UC San Diego have used it on mosquitoes to fight malaria and scientists have begun to use it on human embryos as well.  Crispr is an acronym for Clustered Regularly Interspaced Short Palindromic Repeats which is a relatively complicated way of saying “gene editing tool.”  What Crispr does is it can target certain parts of a strand of DNA and “delete” them from the strand.  In reality they aren’t being “deleted” but “turned off” so RNA doesn’t code it and begin to manufacture proteins for it.  But the real question is why certain people are against gene editing.  Everyone’s seen the movie GATTACA where gene editing is not only commonplace, but discriminatory.  However in today’s world, the fear is much more strongly rooted than a fear of “geneticism” (genetic rascism).  Using Crispr on viable human embryos to edit genes may have undesired effects.  The turning off/on of one gene could result in the unintentional turning on/off of another.  Also, many scientists believe that a parent making decisions for an unborn child can be unethical and unfair if the child did not want those changes to be made.  And who knows, maybe in the future with the continuous use of Crispr and the development of more complex gene editing tools, “geneticism” could be a reality.

Other articles pertaining to Crispr are linked here and here for more information on the subject.

Invaders or Saviors: The Truth Behind “Invasive” Species


With a name such as “invasive” its hard for an emerging species in a new biome to establish a good reputation.  An “invasive species” can be defined as an organism establishing a presence in a newly introduced area not native to it whether by accidental or intentional means.  For the most part, as stated by the New York Times, it has been the general opinion of conservation organizations to either eradicate or eliminate the invasive species.  However, a large number of scientists including Dov Sax and Ken Thompson, both professors of Ecology at Brown University and the University of Sheffield respectively, are beginning to dispute this idea.  Dr. Thompson claims that species have been moving around for centuries and that humans play a large role in their movement.  In a modern era of globalization, it is getting increasingly harder to stop the spread of “invasive” species and climate change is multiplying the number of species considered “invasive” drastically.  Although Thompson’s theory has a large following, it is not universal.  Some “invasive” species are undeniably harmful such as the fungus that causes chestnut blight which decimated thousands of trees across America in the 1900s or more recently the Zika virus spreading rapidly through mosquitoes drawn north by the warmer climates.  It has been discovered that islands and mountaintops are even more susceptible to these species due to their isolation and indigenous population’s lack of evolutionary defenses.  For example the the accidental transport of the brown tree snake to Guam has nearly eliminated the bird population.  However, this general trend has given many nonnative species a bad representation.  For example, monarch butterflies of California prefer to live in the eucalyptus tree which was brought there 150 years ago.  Or the nonnative crayfish pictured above which feeds the migratory wetland birds of Spain.  In fact the term “invasive species” was coined in Charles Elton’s 1958 book The Ecology of Invasions by Plants and Animals drawing from the heightened tensions caused by World War 2.  This term did not gain its modern weight until the 1990s when the field of Invasive Biology began to grow popular.  Despite findings such as the ones by Thompson and Sax, this is still a much highly debated topic in the field of biology.

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You Are What You Eat


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It has been known for some time by scientists that variations in food intake lead to various different gut floras.  However, that theory had only been tested on mice…Until now.  Lawrence David, assistant professor at the Duke Institute for Genome Sciences and Policy, led an experiment that resulted in the discovery that different foods not only lead to different bacteria, but the bacteria themselves experience gene variations.  Although the discovery itself is truly amazing, the celerity at which the changes occur is the most impressive.  University of Chicago’s professor of medicine Eugene Chang specializes in gastroenterology originally thought the changes would take months or even years but the study showed that the changes started to take place within a couple of hours.  There were also changes in the amount of bile acid secreted into the stomach and that microorganisms native to cheeses and cured meats were stronger against this.  The real question is “Why is this relevant?”  To Chang, the first is evolutionary.  Ancient humans who experienced rapid dietary changes could successfully switch from nuts and berries to meat with little gastric distress and maximum absorption of nutrients from even the most unrecognizable foods.  The second is the effects of diet on certain diseases.  Chang, who has been leading a research team to discover the connection between  B. wadsworthia and colitis in mice is yet to apply these tendencies to humans.  However, he believes there could be a connection.  His experiments show just how sensitive the body is to dietary change.  Dramatic changes in ones diet could lead to a brief exposure to harmful diseases such as inflammatory bowel disease.  The experiments are difficult to conduct however because according to David, it’s hard to find even 10 people willing to dramatically change their diets for science.

original article:

similar article on the gut micro biome:

Only the Small Survive

Small fish featured in its natural niche

Small fish featured in its natural niche

With many large species such as giraffes and sharks threatened with extinction, we might not see the likes of them for millions of years.  History has shown that evolution cannot restore large species for tens of millions of years.  Intrigued by this concept, paleontologist Lauren Sallan of the University of Pennsylvania sought to know why small species are able to bounce back much quicker than larger species.  Looking at aquatic life of the Mississippian Period, from 359 to 323 million years ago, she observed that most fish were significantly smaller than their ancestors.  This idea that certain species generally shrink over time is known as the Lilliput Effect, named after an island indigenous to tiny people in Jonathan Swift’s Gulliver’s Travels.  The fossils used in Dr. Sallan’s project fit this description as their ancestors probably perished perished in the deep freeze brought on at the end of the Devonian Period which wiped out an estimated 96 percent of all vertebrates.  However, the Lilliput Effect does not apply to all species.  One species, known as the rhizodontids, included fish that grew to the size of modern day killer whales.  Dr. Sallan concluded that the painfully slow recovery of large species on this planet is due to the ecosystems decimation during mass extinction events.  Although this particular article does not go into depth on why small animals have an easier time “bouncing back” than large ones, Dr. Sallan examined many fossils which prove that creatures shrank dramatically after large-scaled extinctions.  For example, the average size of a shark shrank from about a yard in length to only a mere few inches.  However, later in the article, Dr. Sallan cites her study by saying how smaller vertebrate species produce and diversify more easily contrary to large vertebrate animals dwindling in diversity until species extinction.

Original Article:

Other Interesting Articles:

Hermaphrodites of the Ocean: How Sea Hares Reproduce


Sea hares, from the taxonomic group Aphlysiomorpha, are appropriately named based on there rabbit-like chemosensory appendages.  What makes these creatures so interesting is that they are one of nature’s most well-known hermaphrodites.  That is, they possess both male and female reproductive organs.  Despite having both of these sexual parts, sea horses still require mates in order to reproduce.  In conventional animal mating, certain male traits are developed in order to attract females.  These traits are very hard to distinguish in sea hares.  Biologist Lisa Angeloni of Colorado State University is researching the mating rituals of sea hares.  She believes that the most noticeable trait in sea hare mating is the size of the “female.”  “Male” sea hares frequently look for larger “females” to produce larger clutches of eggs.  This tendency led Angeloni to make the conclusion that as sea hares grow older and larger, they spend more time assuming the female role.  In sea hare mating, there are rare occurrences when mating chains are formed.  Mating chains occur when more than two sea hares are involved in mating.  These chains, when they do happen, most commonly include three to four sea hares but Angeloni claims to have seen a chain of five sea hares.  The coolest part about the sea hare’s mating ritual is that after a “female” is inseminated, it can choose to continue mating as a “male” inseminating a different sea hare.  It’s not everyday people here about organisms that can be both male and female.  If you want to learn about the origin of the term hermaphrodite click here.  It comes from ancient Greek mythology.

Original article:

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