Have you ever wondered how we look and are so different from ancient cavemen, or even
our great ape relatives?
Our lineage drives back centuries across millions of different animals but how did we become
human?
Well, the answer to this is evolution.
In fact, it is hypothesised that all species evolved from LUCA, or the last universal common
ancestor, who was a form of anaerobic bacteria.
But how exactly did LUCA evolve into the vast range of life on earth?
This is a question that plagued geneticists for years, but now it is commonly accepted
that changes, or mutations, in the genetic code drive evolution.
Over the millions of years that life has existed, these mutations have created the diversity
present on earth, such as us!
Understanding this was revolutionary for understanding biology, but Japanese geneticist Susumu Ohno
thought that there had to be more to this phenomenon and that such complex diversity
couldn’t have just developed through small scale mutations.
As such, Ohno proposed duplication of the entire genome of vertebrates and eventually
landed on his 2R hypothesis in that there were two rounds of entire genome duplication
in vertebrate evolution.
In the words of Ohno, whole genome duplication occurs ‘in one fell swoop’ meaning that
all regulatory regions of the gene alongside all of the genetic content are duplicated
simultaneously.
This process was coined by the term polyploidy.
Polyploidy maintains the stability of the genome and the duplication of DNA creates
more base pairs and therefore allows for twice the amount of mutation.
This opens the doors for huge amounts of differentiation and genetic variability which is thought to
have resulted in the huge diversity amongst vertebrates.
Ohno wrote a whole book on this phenomenon, Evolution by Gene Duplication, which has such
driven a variety of additional evolutionary research, an example of which being an investigation
into Fugu, or pufferfish, evolution.
Researchers at the Institute of Molecular and Cell Biology worked alongside researchers
at the University of Cambridge to answer the question, “How has whole genome duplication
affected the evolution of teleosts, specifically Fugu?”
Teleosts are an evolutionary group of ray-finned fish that encompass over 24,000 marine species
and that originally evolved from lobe finned fishes.
These researchers chose to work on Fugu genomes as they have the smallest and most compact
genome of the teleosts making it easier to analyse.
Prior to this, it was established that teleosts had almost double the number of clustered
Hox genes than what was present in mammalian species.
Hox genes drive the development of body plans and as such, the additional Hox clusters in
teleosts posed the question, “Did and when exactly did teleosts experience whole genome
duplication?”
As such these scientists proposed that either a whole genome duplication occurred before
the teleosts separated from lobe finned fish, or that it occurred after and independently
in different lineages.
To test this, they compared the genome of the Fugu to the human genome and searched
for paralogons, which are sets of genes that are from a common ancestor.
Numerous paralogons are evidence of whole genome duplication and as such are a key part
of figuring out this conundrum.
These scientists used numerous computer programs to visualise the sequence of both the Fugu
and human genome and to therefore search for paralogous regions between the genomes.
In total, 468 paralogous regions were found which spanned 6.6% of the entire Fugu genome.
As such, they were able to confidently determine that whole genome duplication did in fact
occur.
However, this does not fully answer their question, with these scientists then constructing
a figurative “molecular clock” to estimate when this duplication occurred.
This “clock” isn’t really a clock, but rather is a way to use the average mutation
rate to infer when species diverged.
Using this method they concluded that teleosts experienced whole genome duplication prior
to separation from lobe finned fish around 350 million years ago, as such proving their
first hypothesis.
Although this all might sound a bit irrelevant to you, understanding evolution is so important
in learning how to better deal with our changing world.
Phenomena such as surviving climate changes, bacterial antibiotic resistance, and extinction
are all evolutionary based.
Understanding all the ways in which evolution works helps us to be able to use evolution
in our favour.
Using this research and methods, another group of scientists discovered that whole genome
duplication occurs in 30% of cancer-causing tumours which allows them to account for this
in cancer treatment and to eventually develop treatments to prevent this duplication and
ideally tumour growth.
Now this is all very theoretical and a long way in our future, but understanding these
things now is integral for our species, so who knows maybe one day your great great great
grandchildren will have double the DNA that you do.