Copypasting genes: The origin of new genetic information


Uploaded by Gigano1986 on 29.03.2010

Transcript:
Copypasting genes:
the origin of new genetic information
by gene duplication.
Opponents of the modern theory of evolution, i.e. creationist and ID supporters,
often argue that mutations do not add new information
to the genome of any organism.
This criticism has the very real potential
to destroy evolutionary theory if it were correct.
If evolution is to be used a scientific explanation the diversity city of life on earth
then it has to account for the increase in genetic information
over the last few billion years.
And if evolution is incapable of meeting this demand
then the theory is falsified.
Unfortunate for the creationists, their criticism is invalid
Evolution can and does produce new information in every simple way.
In fact, this method predicts that we find characteristic footprints
that we can detect in the genomes of various organisms.
Mutation is the engine of the evolution.
The process of mutation is responsible for introducing variations within a genome
by imperfectly replicating the original DNA sequence.
However,
a mutation in an important gene in most cases leads to a loss of function.
An example of this is p53.
P53 is a tumor suppressor protein
that maintains DNA repair
induces cell cycle arrest
or apoptosis (controlled cell death)
whenever the integrity of that the genome has been lost because of DNA damage.
In essence, P53 prevents cells with damaged DNA from dividing.
A mutation in p53 often leads to a loss of all of these function, and can ultimately lead to uncontrolled cell division,
and subsequently cancer.
Strong conservative selection pressures
prevent a mutated gene, like a mutated p53 gene,
from propagating throughout a population
by negatively selecting those individuals
with a dysfunctional gene.
Gene duplication is needed
to allow propagation of a mutated gene.
Gene duplication simply involves copying a gene;
in this example, gene A.
The newly made duplicated gene can then be subject to a variety of mutations
and the original gene won’t be effected,
thus preserving the original function.
The copy gene can diverge rapidly from the original because, unlike its parent gene,
is not subject
to selective pressures
that force the gene to maintain function.
The original gene A maintains its function
because of the conservative selective pressures acting upon it.
The copy gene however can do either of two things:
1) it acquires too many deleterious mutations
and degenerates
into a non-functional pseudogene,
designated
psi A,
or 2) it will acquire mutations
that lead to a difference in expression
or a different property
that is considered advantageous,
and become a new gene,
designated A2.
This new gene, A2,
will there have a related function to the original gene A.
Duplicated genes will give rise to complex genomes,
and can do so quite quickly.
Estimates in a study carried out by Lynch and Conery in 2000
state that the average gene undergoes duplication 0:03:22.889, 0:03:25.359 once every one hundred million years.
This may not seem very quick,
but let me demonstrate a little calculation.
if we were to start off with one gene at 3.5 billion years ago,
and if gene duplication takes place once one hundred million years,
then today
we would have
almost thirty five
billion genes.
While it's not entirely certain how many
different genes exist in the entire world,
this rate is quick enough to account for the huge amount of variation in genes.
Earlier I mentioned finding characteristic footprints within that the genomes of various organisms
that tell us gene duplication has taken place.
The process of gene duplication leaves behind two distinctive marks: 0:04:10.089, 0:04:14.099 1) duplicated genes often have a related function to the original gene
and 2) 0:04:15.289, 0:04:19.690 duplicated genes are often found close together in the genome
Do we really find these characteristics?
The answer is “yes”.
And a perfect example as the globin superfamily.
Globins are proteins that bind oxygen
and are therefore very important
to the respiratory system.
Hemoglobin,
here shown in green and red,
is a well-known and well-studied example.
It is the protein responsible for the oxygen binding property of blood and is found in red blood cells.
But there is also myoglobin which serves as an oxygen transporter in muscle tissues.
And then there are neuroglobin and cytoglobin.
Although the function of cytoglobin has remain obscure since its recent discovery, 0:04:57.119, 0:05:04.690 both cytoglobin and neuroglobin share a homologous relationship with hemoglobin and myoglobin.
When we take a closer look at one particular gene cluster,
the human ß-globin gene cluster,
we can reconstruct its history throughout several species
back to a single gene.
Here you can see that a part of that reconstructed history,
limited to a few species.
As you can see the amount of tweaking done in the last 150 million years
can give rise to a wide variety of new and functional genes
throughout several related species. 0:05:31.959,0:05:33.830 Apart from gene duplication
gene conversion and inactivation also take place.
Gene conversion is the exchange of a sequence from one gene
with a sequence from another.
An example of this in the human cluster are the beta and delta genes.
The beta gene has replaced a part of the delta gene sequence
with a part of its own.
The variety of different globin proteins provides benefits
at different developmental stages
and subsequently became
more and more specialized
in their function.
In this video I hope to have demonstrated that new information can and has been added by
evolution.
By mutating duplicated genes 0:06:13.900, 0:06:18.999 a new gene with a related function to the original can arise.
I’ve also shown you that mutations in the duplicated gene
can go awry
and lead to the formation of non-functioning pseudogenes.
This process leaves behind certain footprints that we can see
and an example of a gene cluster found by looking at those prints
is the globin superfamily.
The criticism we discussed made by opponents of evolutionary theory
would seriously endanger the validity of evolution if it were correct.
However, as we can see
mutations and natural selection can give rise to new genetic information 0:06:49.990, 0:06:54.080 and so the criticism maintained by opponents is invalid,
just like many other the arguments against evolution.
Thanks for watching