Tags: Business Plan For FilmProm EssayIntroduction For A Research Paper ApaTypes Of Methodology For Research PaperDissertation StepsAbortion Essay Works Cited PageDomestic Violence Research Papers
DS individual have variety of physical characteristics like a small chin, slanted eye, poor muscle tone, a flat nasal bridge, a single crease of the palm and a protuding due to small mouth and large tongue .
In Robertsonian translocation which occurs only in 2-4% of the cases, the long arm of the chromosome 21 is attached to another chromosome (generally chromosome 14).
While mosaicism deals with the error or misdivision occurs after fertilization at some point during cell division.
A “critical region” within 21q22 was believed to be responsible for several DS phenotypes including craniofacial abnormalities, congenital heart defects of the endocardial cushions, clinodactyly of the fifth finger and mental retardation .
Dual-specificity tyrosine phosphorylation-regulated kinase (DYRK1A) and regulator of calcineurin 1 (RCAN1), Down syndrome cell adhesion molecule (DSCAM) has been suggested to play a critical role in the developing brain and has also been identified as a candidate gene for the increased risk of CHD in DS individuals [21,22].
Down syndrome (DS) is one of the commonest disorders with huge medical and social cost.
DS is associated with number of phenotypes including congenital heart defects, leukemia, Alzeihmer’s disease, Hirschsprung disease etc.The most common cause of having a DS babies is presence extra copy chromosome 21 resulting in trisomy.The other causes can be Robertsonian translocation and isochromosomal or ring chromosome.Previously a region of 1.6 to 2.5 Mb was recognised as sufficient cause for DS pehnotype [17, 18].The sequencing of Hsa 21 proved to be an important factor in the progression of DS research  and led to further insight into genotype-phenotype correlations associated with DS and precise characterizations of DSCR regions .DS has high genetic complexity and phenotype variability [6-8].Trisomic fetuses are at elevated risk of miscarriages and DS people have increased incidence of developing several medical conditions .Recent advancement in medical treatment with social support has increased the life expectancy for DS population.In developed countries, the average life span for DS population is 55 years .Due to this people with mosaic DS have two cell lineages which contribute to tissues and organs of individuals with Mosacism (one with the normal number of chromosomes, and other one with an extra number 21) .Gene dosage imbalance hypothesis states that DS patients have an increased dosage or copy number of genes on Hsa 21 that may lead to an increase in gene expression [13-15].