BIO156 online / summer – Chapter 13 (part C): testing for genetic disorders

BIO156 online / summer – Chapter 13 (part C): testing for genetic disorders


Hello there. Let’s finish off our last voice over video
for this chapter by talking a little about testing for genetic mutations. So, if you have loved doing Punnett squares,
and learning about disorders that are related to issues with genes, and all that stuff – I
might have just the job of your dreams for you! You might want to consider becoming a genetic
counselor. So, what they do, for example, is that they
give advice to parents about the risk of certain inherited conditions, based on their genotype,
and things like that. They often work with other healthcare providers,
too. The job would also include discussing testing
options, risks, benefits and limitations. And, in general, just helping the families
to make informed choices. And, when we talk about all this we get back
to our good old friend, karyotyping. We remember that a karyotype was this visual
display of chromosomes pairs, as arranged by their size. Other things that we can see are the shape,
number and banding pattern. How do we actually get a karyotype of an unborn
baby? Well, we need to get some cells from that
baby. And, usually these would be either white blood
cells, or using sampling of the amniotic fluid and hoping to catch the fetus’ cells from
it, or doing something called chorionic villus sampling. So, there are a few methods how we can do
this. But, we need some cells from the baby, so
that we can study the DNA from those cells. So, how does the sampling of amniotic fluid
work? Well, we actually use a long needle to withdraw
a sample from the fluid surrounding the fetus, and in that fluid we usually find some cells
from the fetus. And, it is these cells that we really want. This method is relatively safe, and the needle
can be guided by an ultrasound. And, in terms of the safety of this method,
it says a lot that there is only about 0.3% risk of it causing a spontaneous abortion. One of the challenges with this method, though,
is that it cannot be performed until after 14th or 17th week of pregnancy, depending
on a few different factors. Another method that I mentioned was sampling
the cells from where the placenta is developing. And, this is done by suction of some cells
from chorion, which is that site where the placenta is developing. And, we remember that a placenta contains
both mother’s and the developing child’s cells, so this is a way to get cells from
the fetus in a relatively safe manner. One of the benefits of this method is that
it can be performed as early as on the 5th week of pregnancy. However, there is a little greater risk, I
believe 0.8%, of a spontaneous abortion being triggered by this procedure. And, sometimes even if we do not have a concern
about a chromosomal abnormality, based on the family history, we might still wish to
do these tests. This is because they can tell us about more
than 400 different disorders that result from specific genes. Of course, it is important for the genetic
counselor to know about the medical history of the family, so that they can do these pedigrees. And, that work largely determines what tests
are needed. So, what can we test for, at large? Well, we can test for a protein or the DNA. So, we can use either genetic markers or genetic
profiling. One method includes using DNA micro-arrays,
which are basically these small chips made of silicon and they screen at one time for
many, many, many things. And, another option is what I used to teach
for living: ultrasound. So, that is using a high frequency sound waves
to construct an image. And, I believe that we already touched upon
the testing of fetal cells. One more thing that I want to quickly discuss
with you about is these genetic over-the-counter home test kits. And, we watched that cute video about one
of these at the beginning of the last module. But, do remember that it was an advert. And, what you will find out is that there
is a huge number of different kinds of tests available. It seems like everyone is tapping on to this
market. And, there are some really weird ones, too. Like: ‘Test your alcohol tolerance based
on your DNA.’ Or: ‘Lactose intolerance DNA test.’ And: ‘Joint injury likelihood DNA home test
kit.’ And, what else have I seen? I remember, tests for hair and aging of the
skin, and hunger and weight. Well, basically tests for everything imaginable
– and things that you never even knew to imagine. One thing to remember, though, is that they
are not regulated by the FDA. This is, the Food and Drug Administration,
which regulates most of this kind of things. So, there is no standard on the quality or
accuracy of the information that you get out of them. But, if you are not too worried about it,
it can be fun. But, another thing that concerns me, as a
medical professional with some background on these things, is that what happens to your
data. Let’s do an exercise… How many of you really read through the terms
and conditions of an app or a software that you have just installed to your computer? I mean, I will be the first one to admit that
I never do. Ain’t no one got time for that. If you try to read them, they are usually
tens of pages long, and of a legal format text. So, I have no clue what it is about. But, when you click on that agreeing the terms
and conditions buttons, you have to allow whatever is said on those terms and conditions. Who knows, if Apple was to add somewhere there
that: ‘By clicking this you allow us to do whatever we want with your credit card
details.’ I probably would have already signed my life
away. But, the reason why I find this problematic
with these genetic tests is that you would need to be very certain and clear of what
they are going to do with your data that they collect. Because, if your data is not treated safely,
or if it is shared – and, a lot of time you have to provide quite a lot of other information
with these tests – it can open a huge can of worms. Imagine, if you are not tested for it, but
the sample is saved and later on used to find out if you are more likely to develop some
disease. And, if that disease was to be a potential
risk for the employer or an insurance company. And, for that reason you lose out on your
dream job or have to pay more for your insurance. Well, I guess that what I am trying to say
is that you never know. Also, what if a test tells you something that
is a big deal of a negative thing. I would recommend having a medical professional
available to discuss these results with you. But, for the price of these test kits, that
is not unfortunately included. Really, the only thing you own in this world
is your own DNA. And, to give that away, without knowing what
terms you sign, well for me it sounds a bit foolish. I am not trying to discourage anyone from
doing these tests. But, just be aware that there is things to
be considered at least. So, this is where we will finish off the voiceover
presentations for this chapter. And, I have one quick time lapse video for
you to finish this chapter. Let’s see again soon!

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