stated clearly presents
How does new genetic information evolve?
segment 1 point mutations in
Our previous films we learn that genetic information
information contained within a stretch [of] Dna or rNA called a gene helps determine the size
shape and
even the behavior [of] a living creature
Humans have over 20,000 genes which tell our cells how to build and maintain our bodies
The information needed to build a person is obviously different than the information needed to build a mushroom
Biologists however tell us that all living things on Earth including
people and mushrooms evolved from an ancient common, ancestor a
Relatively simple creature with far less genetic information in the plants animals and fungi alive today
If this is true, how did all this new genetic information evolve?
We don't yet know for sure how the very first genes came about but through careful genetic studies of living things in the wild in
the laboratory and
even in our own backyards
We've discovered many ways in which new genetic information evolves today in
This film we'll look at the simplest mechanism
point mutations A
Point mutation is any change that only affects a single pair of nucleotides or letters in the genetic code
They often occur when cells are reproducing they appear to be mostly random, and they're surprisingly common
Current studies suggest that in Humans every child born has Roughly 70 unique point mutations
Most mutations are completely neutral
but if one happens to land in a sensitive spot of genetic code and often has a negative effect on a
creatures ability to survive and reproduce
Natural selection usually takes care of these negative mutations by simply removing them from the Gene pool on
Rare occasions beneficial point mutations occur while the changes they [they] aren't quite as extreme as what we're used to in the movies
Incredible changes have been observed
Researchers in the Lab of Dr.. Richard Lenski
Have observed and documented hundreds of mutations in Bacteria
one of these for [example] was a beneficial point mutation found in a strain of e.coli an
[a] from its code was simply replaced with a t
those who carried the mutation were able to reproduce faster than normal in the lab in
Less than one year they out competed and caused the complete local annihilation of their non-mutant siblings
Back in 1976 two scientists reported a strange mutation in salmonella that occurred in one of their labs
Their work was recently evaluated by Dr.
Michael Behe who classified their discovery as a rare gain of function mutation?
The mutation gave these Microbes the Brand-new ability to detect and then eat a rare sugar called D arabinose?
microorganisms are interesting but what about larger more complex animals can simple mutations give them new features [to]
Most domestic dogs and their wild relatives gray wolves have fairly short fur
Some dog breeds however have extremely long fur
By carefully studying the genetic code [of] over 700 dogs and then comparing their dna to that of wolves
scientists discovered a single point mutation on a gene called Fg F5
This point mutation which simply changed ag to a t is
Largely responsible for the long fur found and dozens of dog breeds including the Shih tzu
the Collie and the Pomeranian
But what about wild plants and animals can [they] undergo positive point mutations as well?
cane Toads and their relatives
produce a Milky toxin and a gland behind their ears that kills almost any animal that tries [to] eat them if
You could zoom in to [see] the surface of a cell inside an animal's body
You would find tiny protein structures that act like pumps embedded in the cell's Membrane or skin
These protein pumps movie electrolytes in and out of the cell
Toad toxins work by attaching to and clogging these pumps wreaking Havoc all throughout a creatures body
Dr.. Nicholas Casewell and his colleagues recently found that several different kinds of animals
Lizards snakes and even hedgehogs
have all independently undergone small point mutations which modify the shape and stickiness of their transporter proteins as
A result toad toxins [fail] to attach meaning that these mutants are now immune to the poison
So to sum things up point mutations are an excellent source of new genetic information
for a population
dog populations of the past for example
only had information for growing short fur
Thanks to a point mutation. They now have information to make pups with short fur or long fur
It's important to note however
Point mutations do not usually increase the total amount of information in the genetic code [of] an individual
Instead they edit what's already there meaning [that] for the individual when new information is gained old information is lost in
Our next film we'll look at a special type of mutation called a duplication event
These mutations dramatically increase the length of the genetic code and can even give rise to entirely new genes
Until then I'm John perry and these were just a few simple examples of how new genetic information evolves
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I'd like to give a special. Thanks to molecular biologist, Dr.. Nicholas. Case well. He volunteered hours of his time advising us on this film
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So long for now stay curious