BCH447 lecture 9
Continuation from lecture 8... It seems that collectively most of our genes
have come from eubacteria... If we look at the sum of all of them.
Doolitle thinks that the first few million years of life had a lot of gene
exchange thru horizontal gene transfer. But afterwords... Several branches
jumped out of the pool of gene exchange.
At some point people believe that there may have been a fusion between archae
bacteria and eubacteria to form the eukaryote. And then at another point, a
bacterium was engulfed by the eukaryote... And we got the mitochondria.
Therefore, we ended up being more eubacteria than archaebacterium.
Later on, another transfer may have taken place in eukaryotes, giving us the
chloroplasts... From cyanobacteria engulfment.
General rule for reading papers... If someone talks about opposing ideas...
These people are more likely to have correct information.
There is really no good answer.
Is there really a tree of life.
An operational definition of epigenetics.
Epigenetics is information other than dna sequence that can be inherited or
is heritable from one generation to the next. The word is ill defined.
The broad definition of epigenetics is all the factors that influence
phenotype that are not defined by dna sequence.
The more common definition is that it is heritable information, passed on,
even though its not dna.
One example used was methylation of genes. If methylation occurs and that
marker is passed onto the progeny, then there is inheritance of a marker that
is not based on dna.
The argument is that epigenetics is so important that we need to rethink our
view of evolution.
But, i mean if i repress and operon and thst repression is passed on... Thats
just gene regulation... How is that epigenetics... Its genes regulating
genes... Thats part of what proteins do.
Methylation in bacterial genomes protect the bacteria from chewing up their
own dna... And allow for the destruction of foreign dna.
During dna replication in bacteria.. One dna strand is methylated... This
gets recognized by the methylase... And it methylates the second sight.
This is heritable, characteristic and its not dna....
So here we are saying that epigenetics is a change in the actions of the cell
that can be reversed but is not related to dna. He believes people are confusing evolutionary theory and the history of life.
Note that all the people