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Genetic Disorders & Errors
Cystic fibrosis, Huntington's disease, Tay-Sachs disease, sickle cell
disease, Down syndrome, and cancer all have something in common. They
are all genetic disorders, and we will discuss why they may occur and what
problems they might cause.
Genetic Disorders & Errors
Genetic disorders are types of diseases that occur as a result of an
abnormality in our genetic code - the code that makes us who we are. If it is
a bit off or massively messed up, then run-time errors result, causing a
person with the genetic disorders a whole slew of problems.
This lesson will point out for you some very well-known genetic disorders,
why they occur, and what that results in, in terms of errors in function of our
body.
Cystic Fibrosis and Sickle-Cell Disease
One very well-known and talked about genetic disorder is known as cystic
fibrosis, a genetic disease that occurs as a result of a mutation in the
CFTR gene. A mutation in this gene causes normally thin and watery
secretions in your lungs and pancreas to become very thick and sticky, like
molasses.
This causes the airways of the lungs to become clogged with abnormal
mucus. The thick mucus results in difficulty breathing and predisposes a
person to bacterial infections in the lungs. Because the ducts of the
pancreas, an organ that makes digestive juices, are also clogged up,
people suffer from malnutrition, because they cannot properly digest and
absorb their food.
Cystic fibrosis is like having the city streets, like airways and ducts in your
body, chock full of molasses. It will be very difficult to move through them,
like it is difficult for air and digestive juices to move through the clogged
passageways as well.
Another very famous genetic disorder is called sickle cell disease, and it
is a blood disorder that results in abnormally shaped red blood cells.
Normally, red blood cells, the guys that carry oxygen throughout your body,
have a nice round shape. But in sickle cell disease, the red blood cells look
like a sickle, as in a hammer and sickle. Or, you can think of them as
having a crescent shape.
These abnormal red blood cells do not live for very long, about 10-20 days,
as opposed to 120 days for a normal red blood cell. Because the number of
dying red blood cells outpaces the amount that can be produced, a person
becomes anemic, or deficient in red blood cells. This is why sickle cell
anemia is just one problem associated with sickle cell disease, and it leads
to a feeling of fatigue, since your body's tissues don't get enough energygiving oxygen delivered to them.
Just think of a sickle cell as a truck transporting energy drinks and food
throughout a country. If the trucks break down days after leaving an
assembly plant, there won't be a big enough supply of working trucks, and
this causes fewer trucks to be on the road, which means there's less food
being delivered to stores. With sickle cell disease, your body isn't getting
nutrition very efficiently, and that means you are hungry more often and as
a result feel kind of tired most of the time.
Down Syndrome, Tay Sachs, & Huntington's Disease
While sickle cell anemia implies a lack of something, a lack of red blood
cells, some genetic disorders have too much of something. Namely, in
Down syndrome, people are born with one extra copy of chromosome 21
and therefore have three, as opposed to two, chromosomes.
Down syndrome is a condition that results in mental disabilities, a small
head, short neck, and flattened facial features. Around half of all people
born with Down syndrome also have a heart defect. Many others are
predisposed to all sorts of other problems, like an underactive thyroid gland
and gastrointestinal disease.
Children born with Down syndrome typically live longer than those that are
born with another terrible genetic disorder, known as Tay-Sachs disease.
This is a disorder where a defective gene on chromosome 15 causes the
destruction of neurons (or nerve cells) in the brain and spinal cord as a
result of fatty substance accumulation. Such a problem will lead to weak
muscles, an inability to sit or crawl, seizures, vision and hearing loss, in
addition to paralysis and death by age 4 or 5.
The destruction of the nerve cells is akin to having the electrical circuitry in
your phone, fridge, or car completely destroyed. None of these things can
function without all that wiring, and that is similar to why a person's body
similarly shuts down under the influence of Tay-Sachs disease.
Another genetic disorder that affects neurons is called Huntington's
disease, a disorder that causes the breakdown (or degeneration) of nerve
cells in the brain due to a mutation in the HTT gene. Unlike Tay-Sachs
disease, which causes problems early in life, Huntington's disease usually
causes symptoms around age 40. People who have this problem have
trouble moving, due to involuntary jerking or muscle rigidity. They also
cognitive disorders, such as difficulty planning their tasks or learning new
information. Psychiatric problems may also occur, such as depression or
obsessive-compulsive disorder.
Cancer as a Genetic Disorder
While plenty of genetic disorders are inherited from a parent, not all have to
be.
Sometimes a person is born just fine, without any significant predisposition
to any one disease. But over time, lifestyle factors may overpower even
some of the strongest genes a person may have and lead to the
development of cancer.
Cancer refers to the abnormal growth, division, and even spread of cells
throughout the body, due to alterations, or mutations, in DNA. Yes, in some
rare cases cancer can be inherited. In other cases, genetic predispositions
to potentially developing cancer also exist.
Overall, though, cancer can develop without the two latter factors. For
instance, smoking, constant sun exposure, exposure to different drugs,
toxins, and even viruses can lead to the formation of cancer even in people
who do not have any overt predisposition to cancer development in
general!
The risk factors for cancer I just named are like evil computer programmers
that hack into your computer code, your DNA, change the sequence of
computer code, and watch with evil glee as pop-up windows multiply en
masse on your computer screen. Except in cancer, it is the body's cells that
multiply en masse.
Lesson Summary
This lesson explored some well-known and important genetic disorders.
First, we took a look at cystic fibrosis, a genetic disease that occurs as a
result of a mutation in the CFTR gene. Cystic fibrosis causes thick and
viscous mucus buildup in many places, including the lungs and pancreas.
We then discussed sickle cell disease, and it is a blood disorder that
results in abnormally shaped red blood cells. Sickle cell disease includes
sickle cell anemia, a condition where there aren't enough red blood cells.
This occurs because the oddly shaped red blood cells die prematurely, far
faster than they can be replaced.
After discussing sickle cell disease, we went on to talk about Down
syndrome, which is a condition that results in mental disabilities, a small
head, short neck, and flattened facial features. Children suffering from
Down syndrome have characteristically shaped faces and heads as well as
intellectual disabilities.
Other children might be born with a very deadly genetic disorder known
as Tay-Sachs disease. This is a disorder where a defective gene on
chromosome 15 causes the destruction of neurons (nerve cells) in the brain
and spinal cord as a result of fatty substance accumulation. Unfortunately,
children born with this genetic disorder usually do not live past ages 4 or 5.
While very young children are afflicted with Tay-Sachs disease, it is usually
adults around the age of 40 or so that begin to have the symptoms
associated with Huntington's disease, a disorder that causes the
breakdown (or degeneration) of nerve cells in the brain due to a mutation in
the HTT gene. This disease causes motor, cognitive, and psychiatric
dysfunction in affected individuals.
Finally, don't forget that cancer is a genetic disease, even if it's not an
inherited form of cancer, because changes in cellular genetic structure, as
a result of outside forces like sunlight and viruses, can cause the cells to
multiply out of control.