Question

What do you mean by chromosomal disorder?

Answer 1

Chromosome disorder: An abnormal condition due to something unusual in an individual's chromosomes. For example, Down syndrome is a chromosome disorder caused by the presence of an extra copy of chromosome 21, and Turner syndrome is most often due to the presence of only a single sex chromosome: one X chromosome.

A chromosome disorder results from a change in the number or structure of chromosomes.

• Each of our chromosomes has a characteristic structure.
• Historically, scientists have used a staining technique that colours the chromosomes into a banding pattern.
• These banding patterns make each of our individual chromosomes easier to identify, like a map.
• A set of chromosomes, as seen under a microscope, is known as a karyotype.
• Any deviation from the normal karyotype is known as a chromosome abnormality.
• While some chromosome abnormalities are harmless, some are associated with clinical disorders.
• Half of all spontaneous abortions are due to chromosome abnormalities.

Numerical abnormalities

• The most severe chromosome disorders are caused by the loss or gain of whole chromosomes, which can affect hundreds, or even thousands, of genes and are usually fatal.
• A few numerical abnormalities support development to term, either because the chromosome is small and/or contains relatively few genes or because there is a natural mechanism present to help adjust gene dosage.