FREE ESSAY ON GENETIC DISORDERS

GENETIC DISORDERS

Chris Grounds CCS
Biology II 10/3/00
Earth's inhabitants have populated all of the regions of the world, discovered places
never dreamed of, and have advanced beyond normal understanding, while man can still be
conquered by an object which is immeasurably small. While man has been so busy trying to
find a way to get rid of all pain and suffering, he has finally discovered that there are
things that cannot be stopped. This relentless phenomenon is called a genetic disorder. A
genetic disorder by definition is a medical condition caused by an error in a person's
genetic material . Genetic disorders play an important role in life and must be learned
about if humans are going to survive.
To fully comprehend genetic disorders, one must understand the basics of genetics and
it's diseases. Some genetic disorders can already be seen at birth, while others don't
show up until in childhood or adult life. In these instances it is usually harder for
them to be identified. These disorders aren't always serious though, they may cause such
a small disease as color blindness or go all the way up to death. There have already been
9000 genetic disorders found and researched by scientists. What makes genetic disorders
really stand out is their complexity. Genetic disorders are known for affecting at least
more than 3 different parts of the body, thus making them harder to cure and more of a
threat. 
All genetic disorders involve genes of the nuclei in some way or fashion. Genes are made
of DNA, Deoxy Ribo-Nucleic Acid, and are arranged specifically on chromosomes.
Chromosomes are tight coils of chromatin, which is made up of DNA. Chromosomes are an
instrumental factor in genetic disorders. Chromosomes are made up of a "p" arm and a "q"
arm. "P" stands for petite or short, while "q" is the next letter in the alphabet, it
means long. Located in the center of the chromosome is something called a centromere,
pinched portion of the chromosome that connects both arms of the chromosome. Normal
humans have 46 chromosomes, which means that they have 23 pairs of chromosomes. 44 of
these chromosomes are normal, while that last two determine the gender of the individual.
To understand chromosomes, a technique was made that could stain chromosomes so that they
could be seen. After this innovation was discovered, a new technique rose called banding.
There are many variations to chromosome banding. Examples of such variations are Q
banding, G banding, and C banding. Each different form uses a separate medium to show the
bands of the chromosome. The bands of chromosomes act as fingerprints, and allow humans
to organized and recognize them. A visual organized representation of chromosomes is
called a karyotype. There are many different variations of karyotypes which go
accordingly with the different chromosomes and genetic codes. A spectral karyotype
distinguishes between chromosomes by color, while a classic one separates by pairing off
in chronological order. 
There are four main areas of genetic disorders, Chromosomal, Single-gene disorder,
multifactorial, and Mitochondrial. Chromosomal disorders affect approximately seven out
of every 1,000 infants. A chromosomal disorder is brought about when a person has too
many or too few chromosomes, or when there is a change in the structure of a chromosome.
Euploidy is the condition of having a normal number of structurally normal chromosomes. A
euploid of any sort has the correct form of product. Aneuploidy is the condition of
having less than or more that the normal diploid number of chromosomes. This condition is
associated justly with cell genetic abnormalities. There are two common forms of
aneuploidy, Monosomy and Trisomy. A monomy is the lack of a pair of chromosomes. An
example of a disease caused by a monomy is Turner's Syndrome. Turner's syndrome is a
monomy of the "x" chromosome. Instead of having two "x" chromosomes there is only one
functioning chromosome. A Trisomy is having three chromosomes of a specific type. A
common trisomy is trisomy 21. Trisomy 21 is Down's Syndrome. The 21'st pair of
chromosomes has three instead of just two. There is another type of aneuploidy called
triploidy. A triploid has three of each chromosome. Most, if not all, individuals that
are born as triploid are either dead already, or will die very soon. A chromosome
deletion is when part of a chromosome has been either deleted or broken off and lost. A
deletion may get rid of an entire chromosome, part of one, or a band. An example of a
disease caused by a chromosome deletion is cri-du-chat. A chromosome duplication is when
a section of a chromosome is duplicated. This is also called a partial trisomy. A new
form of chromosome deformation has been discovered. It is called a chromosome ring. This
is when one end of the chromosome may stick to the other and form a circle which will
cause problems when cell division takes place. Another way this could happen is a form of
cell fusion. A chromosomal translocation is when a portion of a chromosome switches with
another portion and thus making a mixture of two different chromosomes. There are two
different types of translocation, balanced and unbalanced. An unbalanced translocation is
more dangerous because there is probably three pieces of one chromosome, and only one of
another. On the other hand, a balanced translocation shouldn't have that much trouble,
because all of the genetic material is there, however if the individual seeks to have
children, then there are certain risks involved. A chromosome inversion is when there are
two breaks in one chromosome, then the two pieces are switched around, and put back into
the chromosome. There are two different types of inversions. One is pericentric
inversion, which means if the inverted area includes the centromere. If the inverted area
does not include the centromere, then it is called a paracentric version. Chromosomal
disorders are an important part of genetic disorders. 
Single Gene disorders, inborn errors of metabolism or Mendelian disorders, are caused by
non-working genes. Every gene has information used by cells used to manufacture a
specific protein, or a component of a protein. A mistake in the DNA may cause a person's
cells to fail to produce the correct number of a certain protein, or to make the protein
wrong. These kinds of proteins will most likely not work correctly. In some instances, a
faulty gene may have a dominant effect, in which the person has one faulty gene and one
good one, and will have a disorder show up. If it has a recessive effect, then nothing
will happen unless the individual gets two of those genes. Have of all single gene
disorders are autosomal dominant. That means that the messed up gene is carried on an
autosomal chromosome, a normal chromosome numbered one to forty four and excluding the
sex chromosomes. People with this disorder have a fifty percent chance of continuing
their disease onto their children. An example of this disorder would be Huntington's
Disease, which doesn't show up until an individual is thirty or forty. There are also
autosomal recessive disorders. This happens when a person has two faulty copies of the
gene. These parents would have a 25 percent chance of passing it on to their children if
they were both carriers of this disorder. An example of this disorder is cystic fibrosis.
This disorder affects many different regions of the body. Some single gene disorders are
not entirely dominant or recessive and are just called co-dominant. An example of this
disorder is Sickle Cell Anemia. This is when the red blood cells are misshapen and don't
carry enough oxygen and don't move as fast through the vessels. 
There is a single gene disorder which is x-linked. These stem from a gene located only on
the x chromosome. Males have a better chance of receiving these disorders than women. An
example of this disease is Hemophilia, where the body can't clot blood or produce
platelets. 
Multifactorial disorders are caused by gene variations as well as a person's environment.
An example of a multifactorial disorder is neural tube. This is when the structure that
develops the spinal chord and brain is damaged. Some diseases that run in families, but
aren't obviously inherited are thought to be multifactorial disorders. An example of one
of these diseases is coronary heart disease. In these cases a person is predisposed to
get the disease, but a change in lifestyle could affect it and stop it from happening. 
Mitochondrial disorders result from problems with the mitochondria's DNA inside the cell.
Sperm and eggs have mitochondria, but a sperm only gives it's nucleus to the egg, so
mitochondrial disorders are passed solely by the mother. Both males and females may be
affected, but an affected male will not pass it on to his children. Conditions involving
mitochondrial inheritance are rare, though one example is called Leber's hereditary optic
neuropathy. This is a vision disorder that shrinks the optic nerve. 
There are many different ways to tell if someone may have a genetic disorder, these
techniques are called genetic screening. A test that can be done at the earliest part of
life is called the pre-implantation diagnosis, which works with in vitro fertilization,
joining a sperm and egg outside of a woman's body. Physicians can remove a cell from the
embryo to test for a disorder. Prenatal screening, screening done during pregnancy, is
used to identify fetuses that run a risk of getting a genetic disorder. This is done by
testing the woman's blood for specific substances known to be involved in genetic
disorders. Genetic screening of newborn children is necessary to see if the child may
have a disorder that must be dealt with immediately. If diagnosed early enough, an infant
may be treated and have a chance of being cured. Carrier screening is done to see if a
couple are carriers of a disorder before they have children. There are many different
races that run different risks of different disorders. Some receive the disorder more
readily. A family history screening helps identify healthy individuals who may have a
risk of getting a disorder, or passing it along to their children. A doctor takes
information from as far as three generations back to produce a pedigree. The pedigree is
able to help identify the risks of genetic disorders. There is a new form of detection
tool in genetics right now, it is called FISH. This stands for fluorescent in situ
hybridisation. These methods work well and are becoming more popular in detecting
disorders. 
It is necessary the genetic disorders must continue to be studied if man is ever to have
a chance against such a formidable enemy. Currently there are no permanent cures for
genetic disorders. In order to find these cures, there still must be considerable leaps
in the fields of genetic screening and genetic therapy. There is no way that people can
just stumble upon something in such a complex subject as genetic disorders. Although
people still die as a result of man not knowing enough, there is the fact that he never
will. No matter how hard man tries, he can never fully understand something so complex
and perfect as genetics. 
Bibliography
Bibliography
1. Brittanica.com
2. http://daphne.palomar.edu/abnormal/abnormal_1.htm
3. http://arbl.cvmbs.colostate.edu/hbooks/genetics/medgen/chromo.html
4. http://members.aol.com/cdousa/intro.htm
5. www.ich.bpmf.ac.uk/cmgs/fishsg.htm