Down's Syndrome: Causes, Chromosomal Analysis, and Gene Mutation

This assignment provides a detailed insight into the disorder of Down syndrome, depicting the ways how chromosomal aberrations result in the occurrence of the syndrome. It covers causes of the disorder, chromosomal analysis, gene mutation, and considerations for practice and patient education.

Running head: DOWN’S SYNDROME
DOWN’S SYNDROME
Name of the disorder:
Name of the university:
Author note:

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DOWN’S SYNDROME
Executive summary:
Down syndrome is a genetic disorder which is mainly acquired but not inherited from
parents or families. It is important for healthcare professionals to be knowledgeable about the
chromosomal aberrations and mutations that take place in the individuals so that they can follow
the correct treatment procedure. This assignment would provide a detailed insight into the
disorder of Down syndrome depicting the ways how chromosomal aberrations result in
occurrence of the syndrome.

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Contents
Introduction:....................................................................................................................................2
Chromosomal analysis:....................................................................................................................3
Causes of the disorder:.....................................................................................................................3
Origin of the disorder and considerations for practice and patient education:................................4
Gene mutation of the disorder and the way it occurs:.....................................................................6
Conclusion:......................................................................................................................................7
References:......................................................................................................................................8

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Introduction:
Down syndrome is a genetic disorder that takes place mainly due to chromosomal
aberrations. This assignment would mainly comprise of the detailed aspects of chromosomal
analysis of the disorder as well as causes of the disorder. This would also contain the origin of
the disorder as well as the detailed mutations that take place
Chromosomal analysis:
Chromosomal analysis as well as karyotyping can be explained as the test that helps in
evaluating the number as well as the structure of the chromosome of the person for detecting
abnormalities. Chromosomes are thread like structures that remain present within the nucleus of
each cell and contain the genetic blueprint of the body. Each of the chromosomes is seen to
contain thousands of genes in their specific locations and is responsible for the inherited physical
characteristics with profound impact on growth, function and development. Humans are seen to
have 46 chromosomes that are present as 23 pairs. 22 pairs are present in all sexes called
autosomes and one pair is present as either XX in males or XY in males and is called sex
chromosomes (Antonarakis, 2017). All the cells of the body under normal conditions contain the
46 chromosomes except for the reproductive cells like the sperm and eggs that have sets of 23.a
chromosomal karyotyping is the process that helps in examining the chromosomes of the person
for determining if the correct number is present and to find out if each of the chromosomes are
normal or not. When similar testing was conducted in case of the concerned client it was found
that the patient had an extra copy of chromosome 21 in almost all the cells of the body.
Therefore, it was confirmed that the patient was suffering from Down syndrome only.

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Causes of the disorder:
Typically the nucleus of each of the cells contains 23 pairs of chromosomes and half of
them are inherited form each parents. Down syndrome is mainly seen to occur when the
individuals have a full or a partial extra copy of the chromosomes 21. These additional genetic
materials are seen to alter the course of development and cause various characteristics that
remain associated with Down syndrome (Asim et al., 2015). Some of the common physical traits
of the Down Syndrome are low muscle tone as well as small stature along with the upward slant
to the eyes and single deep crease that are present across the centre of the palm. However, each
of the people affected with the disorders can be considered to be unique as they may possess the
characteristics to different degrees or even not at all. A number of different risk factors are
considered by researchers to be the contributing factors for the development of such disorder in
the affected individuals (Stagni et al., 2015). These are the advancing maternal age. Studies
opine that the chances of giving birth to a child with this disorder increase with age. This is
because older eggs have a greater risk for improper chromosome divisions. The risks of a woman
in conceiving a child with the Down syndrome is seen to increase after 35 years of age.
Secondly, being carriers of the genetic translocation of this genetic disorder is another causal
factor. Both men as well as women can pass on the genetic translocation for the Down syndrome
in their children (Karmiloff et al., 2016). Again, those parents who have one child with Down
syndrome or those parents who have translocation themselves remain at the increased risks of
having another child with same disorder.

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Origin of the disorder and considerations for practice and patient education:
In the later period of the nineteenth centuries, john Langdon Down who was an English
physician had provided a good amount of description of a person who suffers from Down
syndrome. This was his scholarly work published in 1866. This helped him to earn the
recognition as the father of the syndrome. In the year 1959, a French Jerome Lejeune had
successfully identified the Down syndrome as a chromosomal condition. He was the one who
first observed that instead of 46 chromosomes, individuals with Down syndrome have 47
chromosomes in the cells. In 2000, one international group of researchers has successfully
identified and catalogued each of the 329 genes present that are present on the chromosome 21
(Grieco et al., 2015). These accomplishments had helped in opening of the door towards the
greater advances in the research of Down syndrome. The concept of single gene inheritance as
well as complex gene inheritance cannot be applied here. This disorder is not inherited but rather
acquired. Moreover, it does not occur due to influence of a single gene or a multiple number of
genes affecting the characteristic traits but mainly occur due to chromosomal aberrations
occurring due to non-disjunction, mosaics as well as translocation. The abnormality is seen to
occur in the egg cells bit rarely occurs in sperm cells. Non-disjunction during cell divisions
causes abnormal number of chromosomes mainly an extra copy of chromosome 21. Extra
genetic materials from chromosome 21 result in development of symptoms of Down syndrome
(Head et al., 2018).
Every parent who is trying to conceive needs to be educated about the risk factors that
can increase the chances of giving birth to a child with Down syndrome. Increased maternal age
like that of above 35 is one contributor and hence should be made known to the parents. Even
parents need to undergo diagnostic tests to find out whether they are carriers of translocators of

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the Down syndromes as this increases the risk of child to be affected with Down syndrome. They
should be educated to consult with genetic counselors that can help them to understand the
chances of parents to have a child with the genetic disorder. They can educate them about the
prenatal tests which can be undertaken and help in explaining the benefits and disadvantages of
the testing. This health literacy can make parents more careful before they conceive children
(Coppeded, 2016).
Early intervention is found to be important for the Down syndrome because individuals
are seen to be at a greater risk of suffering from various health issues as compared to people who
do not suffer from this condition. Most of the associated conditions require medical intervention
right after birth throughout adolescence and even in adulthood. Depending upon the defects
faced by individual patients, particular interventions are applied. Pediatrician, pediatric
cardiologists, gastroenterologists, speech therapists and similar other professionals need to be
refereed (Gardiner et al., 2015).
Gene mutation of the disorder and the way it occurs:
A trisomy is a chromosomal disorder that had been characterized by the additional
chromosome where the affected individual has 47 chromosomes instead of 46. In case of Down
syndromes, trisomy occurs in the chromosome number 21. However, in case of this disorder,
three types of mutations are seen to take place among the various individuals. One of them is the
complete trisomy 21. The researchers are of the opinion that chromosomes line up for dividing
and creating eggs or sperm in the process called meiosis (Beckhaus et al., 2018). In this form of
Down syndrome, non-disjunction is seen to occur. The eggs are developed with two 21st
chromosomes rather than one. Therefore, when such eggs get fertilized, it is seen to contain total

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three chromosomes in place of one. This is the most common ways of developing Down
syndrome. Another form of the disorder is the translocation trisomy 21. In the translocation case,
there remains tow copies of chromosome 21 but extra material from that of a third 21
chromosomes gets attached or translocated to another chromosome. This type of Down
syndrome might occur either before as well as after conception and in this way they might
sometimes be passed down or inherited. Another form of mutation that might occur is called the
mosaic trisomy 21. This is the least common form of Down syndrome. It is seen to occur after
conception for different unknown reasons and might differ from the other two types of trisomy
21 as not all but some cells have the extra copy of the chromosome 21. Therefore, the
characteristics of affected individuals with mosaic Down syndrome are not as much predictable
as those of complete and translocation trisomy 21.
The above mentioned procedures by which mutation takes place in the affected
individuals can shed light on reaching the conclusion about whether Down syndrome is acquired
or inherited. All the three types of Down syndrome are because of genetic conditions but only 15
of all the cases of the disorder have a hereditary compound. Heredity is only found to be factor in
the case of the disorder resulting from translocation accounting for 1% of the cases where there
remains the chance of the mutation occurring before conception (Hithersay et al., 2017).
Heredity is never considered to be the factor in trisomy 21 that occurs due to non-disjunction as
well as mosaicism where the mutation takes place during conception.
Conclusion:
Down syndrome mainly takes place due to trisomy of chromosome 21 resulting in
negative impacts in the affected individuals. It is mainly acquired genetic disorder mainly

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because the chromosomal aberrations take place during cell divisions. Only one percent of the
cases occur due to inherited factor where parents act as carriers of translocators. Healthcare
professionals need to educate parents to prevent such cases successfully.

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References:
Antonarakis, S. E. (2017). Down syndrome and the complexity of genome dosage
imbalance. Nature Reviews Genetics, 18(3), 147.
Asim, A., Kumar, A., Muthuswamy, S., Jain, S., & Agarwal, S. (2015). Down syndrome: an
insight of the disease. Journal of biomedical science, 22(1), 41.
Beckhaus, A. A., & Castro-Rodriguez, J. A. (2018). Down syndrome and the risk of severe rsv
infection: a meta-analysis. Pediatrics, 142(3), e20180225.
Coppedè, F. (2016). Risk factors for Down syndrome. Archives of toxicology, 90(12), 2917-
2929.
Gardiner, K. J. (2015). Pharmacological approaches to improving cognitive function in Down
syndrome: current status and considerations. Drug design, development and therapy, 9,
103.
Grieco, J., Pulsifer, M., Seligsohn, K., Skotko, B., & Schwartz, A. (2015, June). Down
syndrome: Cognitive and behavioral functioning across the lifespan. In American Journal
of Medical Genetics Part C: Seminars in Medical Genetics (Vol. 169, No. 2, pp. 135-
149).
Head, E., Helman, A. M., Powell, D., & Schmitt, F. A. (2018). Down syndrome, beta-amyloid
and neuroimaging. Free Radical Biology and Medicine, 114, 102-109.

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Hithersay, R., Hamburg, S., Knight, B., & Strydom, A. (2017). Cognitive decline and dementia
in Down syndrome. Current opinion in psychiatry, 30(2), 102-107.
Karmiloff-Smith, A., Al-Janabi, T., D'Souza, H., Groet, J., Massand, E., Mok, K., ... &
Tybulewicz, V. (2016). The importance of understanding individual differences in Down
syndrome. F1000Research, 5.
Stagni, F., Giacomini, A., Guidi, S., Ciani, E., & Bartesaghi, R. (2015). Timing of therapies for
Down syndrome: the sooner, the better. Frontiers in behavioral neuroscience, 9, 265.