There are several possible causes:
* May be caused by a mutation, as many cancers.
* There are genetic disorders caused by duplication of chromosome as in Down Syndrome,
or repeated duplication of part of chromosome as in Fragile X Syndrome.
or repeated duplication of part of chromosome as in Fragile X Syndrome.
* The are genetic disorders caused by a deletion of a region of a chromosome as in the
deletion syndrome in which the end of the long arm of chromosome 22 is absent.
deletion syndrome in which the end of the long arm of chromosome 22 is absent.
* The gene defect can be inherited from parents. In this case the genetic disorder called
hereditary disease. Can be happen often healthy parents are carriers of a recessive defect,
although it also occurs in cases with dominant genetic defects.
hereditary disease. Can be happen often healthy parents are carriers of a recessive defect,
although it also occurs in cases with dominant genetic defects.
URL: http://es.wikipedia.org/wiki/Enfermedad_gen%C3%A9tica
Mutation
The mutation in genetics and biology, is an alteration or change in genetic information(genotype) of a living and therefore, will produce a change in the pattern, which occurs suddenly and spontaneously and that can be transmitted or pass on the offspring. The genetic unit is able to mutate the gene is the unit of hereditary information that is part of the DNA. In multicellular beings, mutations can be inherited only when they affect the reproductive cells.
URL: http://es.wikipedia.org/wiki/Mutaci%C3%B3n
Chromosome
Chromosomes are the carriers of most of the genetic material and determine the organization of life and hereditary characteristics of each species. Mendl's experiments showed that many of the characters of pea depend on two factors, later called genes of which each individual receives a copy from the father and a mother.
URL: http://www.iqb.es/cancer/g006.htm
