Genetic Disorder and Disability | Report

Running head: GENETIC DISORDER AND DISABILITY
GENETIC DISORDER AND DISABILITY
Name of the student:
Name of the university:
Author note:

GENETIC DISORDER AND DISABILITY
1
Introduction:
With the global burden of disease, intellectual disability has emerged as one of the
leading cause of premature morbidity around the globe. Down syndrome is considered as the
leading cause of intellectual disability that contributed to a range of other health issues such as
leukemia, neurological disease, congenital heart diseases, difficulties in attention and analysis.
Smith, Næss and Jarrold (2017), suggested that individuals with Down syndrome are affected by
a range of phenomenon resembles other chronic genetic diseases which make it challenging for
the researchers to understand the direct link between genetic factors and phenotypes.
Considering the global statistics, according to the world health organization, the approximate
incidences of Down syndrome is 1 in 1000 individuals where the United States has emerged as
the country with the highest incidence of Down syndrome (Kazemi, Salehi and Kheirollahi,
2016). While the limited study had conducted in Malaysia regarding Down syndrome, the recent
statistics suggested that in Malaysia, 1 out of 981 individuals are suffering from Down
syndrome. The majority of individuals with Down syndrome have an extra copy of chromosome
21 which resulted in phenotypic changes amongst patients. Zahari et al. (2016), suggested that
trisosomy21 occurs due to failure of chromosome separation during e gametogenesis that
resulted in the extra chromosome. Consequently, infants with Down syndrome experience
intellectual, developmental or neurological disabilities that hindered them to live a healthy and
purposeful life. While the occurrence of other autosomal trisomy is more frequent compared to
the 21, but the postnatal survival rate is low for other autosomal trisomies as compared to Down
syndrome. The essay aims to provide an in-depth analysis of Down syndrome as a genetic
disorder, the impact of disease order on the physical, developmental and psychological
development of the children in the following paragraphs.

GENETIC DISORDER AND DISABILITY
2
Discussion:
Explanation of the selected genetic disorders among children:
While a range of intellectual disabilities observed amongst children, Down syndrome has
been chosen for this essay. Antonarakis (2017), suggested that Down syndrome is considered as
a genetic disorder of infants where trisomy of 21 observed that resulted in altering gene
expression. A range of hypothesis related to the genetic basis of Down syndrome and the
association of phenotypes was presented by different researchers. While few researchers
hypothesized that a genetic dosage imbalance resulted in an increased dosage of Hsa21 and gene
expression, other researchers hypothesized that genetic imbalance amongst the children was
formed by diverse trisomy gene and influence the expression of many genes (Antonarakis et al.,
2017). However, the common hypothesis for the developing Down syndrome is multiple critical
genes play a crucial role where DSCR on 21q21.22 is accountable for various clinical
manifestation of Down syndromes amongst the children. Playas (2017), highlighted that
chromosome 21 is the smallest human chromosome which contains approximately 200 to 300
genes. The genetic basis of Down syndrome is that three cryptogenic forms of trisomy 21
resulted in clinical features of a down syndrome such as free trisomy, Robertsonian translocation
trisomy 21 and mosaic trisomy. The genetic abnormality observed amongst children when high
gene expression of genes of trisomy 21 resulted in overexpression in cells and tissues of the
children with Down syndrome. Consequently, children with Down syndrome exhibit
phenotypical abnormalities. The reproductive biology suggested that Down syndrome observed
when a part of chromosome 21 attached to another chromosome during the process of
translocation (Santoro et al., 2017). In the very early development of foetal the formation of 21
trisomies is highly prevalent. The affected individuals usually have two normal copies of 21

GENETIC DISORDER AND DISABILITY
3
chromosomes along with another 21 chromosomes attached to any of the normal copy. On the
other hand, limited population exhibit mosaic 21 where few chromosomes of cells carry trisomy
21 compared to other normal chromosomes. The molecular biologist suggested that partial
duplication of Down Syndrome Critical Region (DSCR) within 21q22 is responsible for the
development of the Down syndrome.
Figure: down syndrome ( trisomy 21)
Source: (Antonarakis et al., 2017).
Carozza et al. (2016), suggested that the frequent risk factors for Down syndrome
include advanced maternal age, first born with Down syndrome, family history of Down
syndrome and carrying the genetic translocation for Down syndrome. Advancing maternal age is
considered as the most common risk factors for the Down syndrome amongst offspring since
older eggs are at high risk of undergoing improper genetic division (Kazemi, Salehi and
Kheirollahi, 2016). Therefore, the children with Down syndrome and associated abnormal
phenotypes conditions can inherit Down syndrome from the unaffected parents. The extra-