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Child psychology

March 24, 2016 | Author: | Posted in psychology, social sciences

Down syndrome , also commonly know as Trisomy 21 , is a genetic condition resulting in the presence on part or all of an extra 21st chromosome This is characterized by a grouping of both major and minor anomalies of body structure and function (Roizen Patterson , 2003 . Impairment of learning and physical growth , as well as facial appearance is present in the majority of cases (Roizen Patterson , 2003

Most cases of Down syndrome are not inherited , but occur as random events during the formation of the reproductive cells , both eggs and sperm . An error [banner_entry_middle]

in cell division call nondisjunction results in reproductive cells with abnormal number of chromosomes (National Library of Medicine , 2006 . For instance , either an egg or sperm cell may contain an extra copy of chromosome 21 . If this cell contributes to the individual ‘s genetic makeup , the individual will have an extra copy of chromosome 21 in every cell in their body (National Library of Medicine 2006 . An unaffected person can carry a rearrangement of genetic material between chromosome 21 and other chromosomes . This is called a balanced translocation . Even though , this individual shows no signs of Down syndrome , individuals who carry this type of balanced translocation are at a greater risk of having a Down syndrome child (National Library of Medicine , 2006

Individuals who carry Down Syndrome will have all or some of the following physical characteristics : muscle hypontia , oblique eye fissures that has a small skin fold on the inner corner , flat nasal passage , enlargement and protrusion of the tongue , relatively short neck , white spots within the iris , excessive flexibility within the joints , congenital heart defects , and single flexion furrow of the fifth finger (Wood , 2003 . Individuals with Down syndrome also have mental retardation in the mild to moderate IQ

range (50-70 35-50 . However , individuals with Mosaic Down Syndrome can have IQ scores up to 30 points higher (Wood , 2003

The chromosomal abnormality is characterized by the presences of an extra copy of genetic material on the 21st chromosome . The effect due to the extra chromosome differs from individual to individual and by numerous factors , including genetic and environmental factors (Mitelman 1995

Mosaic Down syndrome can occur when a nondisjuction during an early cell division in a normal embryo , which leads to fraction of the cells with Trisomy 21 . Mosaic Down Syndrome can also happen when the Down syndrome embryo undertakes nondisjunction and cells in embryo revert back to the normal chromosomal arrangement (Leshin , 2000 . There is evidence that Mosaic Down Syndrome can produce a lesser developmental delay than Trisomy 21 (Leshin , 2000

Mosaic Down Syndrome is discovered through genetic testing where 20-25 cells are examined . Due to the cells in Trisomy 21 are all infected , if only some are affected than the diagnosis of mosaicism is determined (Leshin , 2000 . If suspected and not confirmed through blood testing , a skin and bone marrow test are commonly the next line in detection (Leshin , 2000

A chromosomal mutation – centric fusion – can cause Down syndrome known as Robertsonian translocation . In… [banner_entry_footer]

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