Diseases Mental

How Common Is Mental Retardation At Birth?

Mental retardation through genes

Certain genetic disorders are linked to mental retardation, severe health issues and developmental delay. Since the human body is so complex there are no simple answers to the query what makes mental retardation actually. It is attributable to different situations, impairing growth of human brain before or during delivery or in childhood time. Till this time, around 50% of individuals with mental retardation are found to be having more than one casual factor. Certain research also determined that in 75% of kids with minor mental retardation the reason is still not identified. The genetic field has significant implications for persons with mental retardation. Around 350 inborn faults of metabolism are discovered, most of which causes mental retardation. However, the chance to being born with retardation effects of increasing the situation later in life may be due to multiple elements unrelated to human genetic make-up.

Mental retardation through hereditary

As the human brain is a complicated organ, there are lots and lots of genes included in its development. As a result, there are many genetic reasons for mental retardation. Almost all diagnosable reasons of chronic mental retardation derive from genetic disorders. Around 60% of chronic mental retardation occurs due to genetic causes that make it most common reason in cases of chronic mental retardation. Persons with minor mental retardation are not probably inheriting mental retardation as like people with chronic mental retardation. Mild mental retardation occurs most probably due to environmental elements such as personal health habits, nutritional state, socioeconomic level, non-access to healthcare, exposure to chemicals and pollutants etc. Two most general genetically transmitted types of mental retardation are fragile X syndrome and Down syndrome.

How genetic disorders become hereditary?

Genetic diseases can be hereditary in 3 common ways – recessive, dominant and X-linked (Sex-linked). Recessive inheritance takes place when both parents posses a disease-making gene but externally display no symptoms of disease. Children with recessive issues are known as ‘carriers’ as each parent holds one copy of an ailment gene. When these parents give birth, children have a 25% chance to have both ailment genes and being struck. Children also have a 25% chance to have two sound genes and not get struck, and a 50% chance to be a bearer of the disorder, similar to their parents. Identified examples of recessive genetic disorder that are linked to mental retardation include galactosemia and phenylketonuria.

Dominant inheritance happens when one parent holds a disease-causing, dominant gene that creates abnormalities even if mated with a sound gene from the spouse. Under this kind of genetic disorder, children have 50% chance to get the disease-making gene. Popular case of dominant inheritance linked to retardation effects is tuberous sclerosis. X-linked hereditary pattern affects those genes set on X chromosome and may be X-linked dominant or X-linked recessive.

How common X-linked recessive disease is than X-linked dominant hereditary pattern?


X-linked recessive disease is commonly called as sex-linked disorder as it includes genes set on X chromosome. It happens when an un-struck mother possesses a disease-making gene on around one of X-chromosomes. As females have 2 X chromosomes and they are often unaffected as the X chromosome does not contain the disease-making gene makes ups for X chromosome that makes. So, females are less probable to display any signs of the disorder than males except when both X chromosomes possess disease-making gene. Certain cases of X-linked heritage linked to mental retardation include Hunter syndrome, fragile X syndrome, Duchenne muscular dystrophy and Lesch Nyhan syndrome.

By Nikky Prasad, published at 02/12/2012
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