Most dwarfism-related conditions are genetic disorders; however the causes of some disorders are unknown. The majority of occurrences of dwarfism result from a random genetic mutation in either the father's sperm or the mother's egg — rather than being in one of the parent's whole genetic makeup.
• Achondroplasia
Around 80 percent of people with achondroplasia are born to parents of average height. A person with achondroplasia and with two average-size parents received one mutated copy of the gene linked with the disorder and one normal copy of the gene. A person with the disorder might pass along either a mutated or normal copy to his or her own children.
• Turner syndrome
Turner syndrome happens because of a random deletion or severe alteration of an X chromosome, either in the sperm or egg. (The X chromosome is one of two chromosomes that decide the sex of a person. A female inherits an X chromosome from every parent, and a male inherits a Y chromosome from his father and an X chromosome from his mother.) A girl with Turner syndrome has merely one fully functioning copy of the female sex chromosome rather than two.
• Growth hormone deficiency
The cause of growth hormone deficiency could sometimes be traced to a genetic mutation or injury, but for most people with the disorder, no cause can be identified.
Other causes of dwarfism comprise deficiencies in other hormones and poor nutrition.
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