Stated Clearly presents: How do new genes evolve? As we've learned in previous animations a gene is a long stretch of DNA
containing information that codes for something, usually a protein or a group
of proteins. Point mutations can edit small bits of information within a gene.
modifying the type of protein it builds small bits of information within a gene.
modifying the type of protein it builds these small edits are extremely important
for evolution but if we compared the genes of say, a flower to those of a dolphin,
we see that even though they do have many genes in common, dolphins also have entirely new genes that flowers do not have. Flowers also have genes that can't be found in dolphins. This observation forces to ask the question: How do entirely new genes
evolve? Point mutations are clearly not enough. Well, it turns out that over the
years, scientists have discovered many natural mechanisms for the evolution of
new genes. one of the most common and
well-understood pathway is a duplication event followed by further
mutations. A duplication event is a special type of mutation where, as you
may have guessed, a stretch of genetic code is duplicated and reinserted into a
creature's DNA. Duplications happen naturally all the time, they can be small,
a few letters or nucleotides long. Other times enrtire genes can be duplicated,
dramatically increasing the length of a creatures genetic code. During duplications and in the
generations that follow, further mutations can occur in the new gene
giving rise to entirely new genetic information. Information that codes for
new proteins with new functions. Scientists have directly-observed
duplication events in the lab many times over, because of this they can now
examine the genetic code of any living creature, look for known signatures of
past duplication events, and begin to piece together an understanding of how
specific genes likely evolved. Here we'll look at three traits which arose
from gene duplications. The dachshunds odd-shaped yet powerful legs, the unique
digestive enzymes of leaf eatin monkeys, and finally, the evolution of snake venom!
At first glance you might be tempted to think that the dachshunds short legs are
simply a disability. To the contrary the unique shape of this dog's legs make it
it a surprisingly powerful digger and most importantly, allow it to enter small burrows to coax out rabbits, groundhogs and even Badgers from their dens. Other dogs can
only dream of such adventures. By looking at the dachshunds DNA, researchers have
found that their unique legs are the result of a duplication event! A gene
called FGF4 for was copied and inserted elsewhere in their DNA. The new gene happens to produce protein
in a way that interacts with their growing bones, reshaping the dog's legs
and opening up an entirely new hunting niche for the animal. Humans who liked
the trait, bred the original dog with many others, eventually giving rise to
several new dog breeds and proving that sometimes, even the strangest of
mutations, within the right environment, turn out to be extremely beneficial!
Now let's look at the fascinating case of the leaf eating monkey from vietnam: the Duke lungur. Several species of Asian monkeys eat almost nothing but leaves, a
diet that would cause humans and most other primates major stomach problems.
The monkeys achieve this amazing feat of digestion with the help of several
adaptations, one of which was first made possible by a gene duplication. RNase1
is a protein found all throughout your cells and blood. Experiments have shown
that this protein helps our cells fight against viruses by attaching to and
breaking down virus genes. In your intestines, RNase1 does a similar task but for a very different purpose. There it breaks down genes from the cells of
the food you've been eating, converting those genes into nutrients that your
body can absorb. In humans, the pH or acid levels of your intestines are pretty much the same as the pH levels of your cells. This allows a single version of
RNase1 to work great fighting viruses in your body, and digesting food inside
your intestines. In leaf eating monkeys, however, the intestines are more acidic.
this acid appears to be helpful for breaking down the tough cell walls of raw leaves, but unfortunately, the extra acid also slows down RNase1 proteins which are extremely sensitive to acid. Scientists have found that a
relatively recent duplication in the monkeys RNase1 gene has fix this
problem. The original gene still makes normal
protein to help fight against infections, but the new gene, after being duplicated,
began accumulating mutations that slowly made it better and better at functioning
in acid. Here we have a clear case of a single gene that was once ok at two
separate jobs, was then duplicated, and the two genes of since specialized to
produce proteins for different tasks. Now for an exciting yet slightly disturbing
example: The evolution of snake venom! Genes inside the saliva glands of most
creatures, humans included, produce special proteins that are able to start
breaking down food on a chemical level, even before it gets to the stomach. Venomous snakes, however, have taken this a step further. Their saliva glands produce venom! A cocktail of proteins and other
molecules that kill their prey when injected. Let's see how one of these
deadly proteins evolved, Many people assume that blood clots form when cuts
are allowed to dry in open-air. Amazingly Clots actually form through a series of
chemical reactions that can quickly seal the wound, even underwater. This ability is possible in part because of a protein called factorX. It's found in the blood
of many animals including fish, frogs, snakes, birds, and even people. FactorX normally exists in a dormant or sleeping state, drifting about the bloodstream with no effect. When a blood
vessel is cut, however, chemicals in the damaged tissue activate factorX at the
scene of the injury. FactorX then initiates a series of chemical reactions,
causing a clot to form in seal the wound. The saliva of the Australian
rough scaled snake is loaded with pre activated factor 10 proteins! If the snake
bites an animal, injecting its saliva directly into the wound, rapid clotting
occurs throughout the victim's body. The result is often death! When scientists
look at the genes that code for this protein, they see clear signs that the
snakes very own factorX gene, the one that it uses in its own blood, was copied
through a duplication event. After or during duplication, mutations in and near the new gene cause it to produce factorX protein in the venom glands instead of the blood. As time went on, small mutations built up
in the duplicated gene, making it more and more efficient and its deadly new
task! Here we see that a gene once used for healing, has now evolved to kill! So
to sum things up - how is it that new genes evolve? One of the most important
and well-understood pathways is for genes to duplicate and then accumulate
new mutations. Gene duplications, in combination with similar mutations like
insertions deletions and point mutations, are happening naturally right now, all
throughout the living world. With these mutations constantly occurring and
constantly filtered through natural selection, there are no limits to the
variety of new genetic information, new traits, and new species that
evolution can produce! I'm John Perry and that's how new genes evolve, Stated
Clearly! This animation was funded in part by
GeneTools LLC. They produced molecules called morpholinos that allow researchers
to selectively silent any gene to investigate the effects on cell growth,
tissue, and even cancer. Learn more on their website at gene-tools.com
This animation is also supported by our contributors on Patreon! If you found
this video helpful and would like to give back, visit us at statedclearly.com and
click "contribute" to learn how. So long for now, stay curious!
