About Down syndrome (Trisomy 21)
A genetic messaging system
It is extremely difficult to define intelligence, because it takes on many forms: intellectual, emotional, psychic, etc. Of course, the presence of an extra chromosome 21 affects the neuronal pathways and therefore the intellectual development of patients afflicted with Down syndrome (trisomy 21). However, environment also plays an important role in developing their abilities.
The organism relies on DNA to produce its essential building blocks: proteins. These are produced according to the sequences, or codes, specifically determined by the genes. There are approximately two metres of DNA in the nuclei of cells, which are a mere several micrometres in size!
When chromosomes get mixed up
The chain of events from the strands of DNA to the production of proteins is a complex one. Chromosomes are the most condensed form a DNA molecule can take. Changes in the sequence or number of genes or chromosomes can cause protein dysfunctions. Genetic diseases are the result of change (s) to the genome (set of all genes) causing a pathological process for the individual. This can involve alterations to one or more genes.
Down syndrome (trisomy 21) is the most common genetic disease. It is caused by a chromosome abnormality defined by the presence of an extra copy – either complete or partial – of chromosome 21.
Persons afflicted by Down syndrome (trisomy 21) thus have extra genes: 23 pairs of chromosomes + 1 extra chromosome 21, totalling 47 chromosomes. Chromosome 21 carries more than 400 genes. The counterpart of this chromosome wealth is an imbalance of certain proteins affecting the patients’ cognitive functions.
A spotlight on research
Down syndrome (trisomy 21) operation