Biotechnology: Genetic Modification, Cloning, Stem Cells, and Beyond


It’s Professor Dave, let’s explore biotechnology. In this biology series we’ve learned a lot
about cells, their structure, and the genome within. Along with a sophisticated understanding of
any science comes not just an enhanced worldview, but also the opportunity to apply this knowledge
in order to create technology. This represents our ability to shape the world
as we see fit. There are certainly profound ethical implications
that emerge when we begin to tamper with life. Some say we shouldn’t play god, whereas
others believe we were destined to do just that. This discussion goes beyond the scope of this
course, so let’s instead just go through a summary of some of the incredible technologies
we have been able to develop in the 20th and 21st centuries through an enhanced understanding
of biology. The first key to biotechnology was learning
about DNA and what it does. Once we had this comprehension, we set about
trying to sequence the genome of humans and other organisms. This is the incredible task of documenting
the precise sequence of base pairs in every single chromosome of a cell. Given that this includes many billions of
base pairs, it seems utterly daunting, but the sequencing of the human genome was completed
in 2003. Since then, a variety of different sequencing
techniques have been developed to make this process faster and cheaper, and we have been
able to sequence the genomes of thousands of other species. What can we do with this information? For starters, we can sequence the genome of
cancer cells to find out exactly where the mutation is, and then develop strategies to
combat that particular form of cancer. We can identify genetic susceptibility to
a variety of diseases, and diagnose others, so that individualized treatment can precede
the onset of symptoms. We can gain valuable insight into bacteria
and other pathogens, so we know how to fight them. Beyond this, our understanding of DNA has
allowed us to make copies of any gene we want. This is called DNA cloning. To do this, instead of laboriously synthesizing
strands of DNA, we put bacteria to work, since they have all the machinery that nature evolved
to copy DNA in the first place. Let’s say we have a gene of interest that
we want to learn more about. We can take a plasmid, or circular DNA molecule,
from a bacterium like E. coli, and insert our gene into the plasmid. This is now called recombinant DNA, because
it contains DNA from two different sources, the bacterial genome, and the gene we are
studying, which could be from any organism. Then we put the plasmid back into the bacterium,
and as it divides over and over again, it copies all of the DNA each time, including
our gene of interest. This is highly efficient because the bacteria
do all the work, and they do it very fast. Don’t worry, they don’t mind helping out. Another method for copying or amplifying DNA
sequences is called the polymerase chain reaction, or PCR. This is done by taking some double-stranded
DNA sequence and heating it up so that it denatures, meaning that the strands separate. Then things are cooled to a specific temperature
so that DNA primers can anneal, and then a heat-stable form of DNA polymerase goes ahead
and extends the primers from 5-prime to 3-prime until all the DNA is copied. We now have two copies of the DNA molecule. We use this special polymerase because normal
polymerase would denature at these hot temperatures that are needed to get the DNA strands to
separate. This cycle will then repeat over and over,
yielding four copies, then eight, and so forth, growing exponentially until there are billions
of copies within a few hours. This technique is often used to generate a
supply of a particular DNA fragment that can be used in the cloning technique we described
earlier, since this is how we can get the fragment to include a restriction site that
matches the one in the plasmid where this DNA will be inserted, as we need certain enzymes
to know how to chop things up and put them back together the way we want them to. Once we have all of these genes copied, what
do we do with them? Well, we can do a wide variety of things. We can harvest all of the copies of our gene
and insert them into some other organism, to provide pest resistance to some plant,
or engineer microbes that can clean up ocean waste. Or, we can harvest the products of all this
gene expression, like insulin or human growth hormone, which we can use to treat various
diseases. Beyond cloning genes, we have also figured
out how to clone entire organisms. This is called organismal cloning. This was first achieved in the 1950’s with
plants, where already differentiated cells from a carrot were taken from the root, which
then were able to dedifferentiate and divide, leading to the production of a new genetically
identical carrot plant. More studies of this type led to the cloning
of other organisms through nuclear transplantation, including the famous lamb, Dolly, in 1997,
and other animals like cats, dogs, and cows since then. Cloning technology also led to an interest
in stem cells, which are unspecialized cells that can divide indefinitely and become cells
of any type. This is an area of study with great promise
in curing conditions dealing with damaged tissue, including spinal cord injury. For this reason, human cloning has been an
area of heavy research, so as to produce stem cells for the treatment of conditions ranging
from diabetes to Parkinson’s. But the morality surrounding the cloning of
embryonic stem cells is a gray area, so research has turned largely to induced pluripotent
stem cells, which are differentiated cells that have been reprogrammed to act like embryonic
stem cells, therefore removing any ethical haziness associated with utilizing actual
embryos. This was first achieved in 2007 with skin
cells from a mouse, and since then with human skin cells. With all of these technologies and more on
the way, human potential seems truly limitless. We are exploring gene therapy, and other techniques,
which hold the promise of bringing total immunity to all disease. We are discovering how we might eradicate
the aging process, in effect manufacturing immortality. Will we figure out how to do this, and should
we? It’s difficult to say, but we must remember
that although the future may seem scary, the present would seem just as terrifying to anyone
from the past. Cars and planes that drive themselves using
tiny machines that can think, this is enough to put someone from the 17th century into
a fear-induced coma. So for the sake of our species, we must boldly
go forward into the future, intrepid as we have always been, drawing ever closer to the
ultimate destiny of mankind, whatever that may be.

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