What is fragile x syndrome?
The fragile X syndrome is a genetic disorder associated with mental retardation, autism-like require together with oft sure physical characteristics. The syndrome is caused past times times a mutation inward a cistron (FMR1) which is located on the X-chromosome. About 1 inward 1,500 males together with 1 inward 2,500 women have got this syndrome; that inward the Netherlands virtually 2300 people every solar year xx boys together with fifteen girls born with fragile X syndrome. This makes it, inward the following Down syndrome, the most usual genetic crusade of mental retardation.
History together with name
In 1943 Martin together with Bell described a venture unit of measurement of mensuration with a sex-linked (ie, the condition affects mainly boys) inherited shape of mental retardation. Later, it could alive shown, that this venture unit of measurement of mensuration suffered from the fragile-X syndrome. In 1969 it was discovered that this syndrome was associated with a peculiarity of the X chromosome. When cells are cultured (e.g., from blood or skin) of patients with Fragile X Syndrome inward a nutrient medium with depression folic acid, occurs inward the X-chromosome of a part of the cultured cells of a suspension at the finish of the long arm . So hither is a "fragile site" a vulnerability, which the syndrome its name. In 1991, 1 endure discovered the FMR1gen which is located on that spot, together with the divergence that causes the syndrome.
What causes fragile x syndrome?
The fragile X syndrome is caused past times times a change, mutation inward the FMR1 gene, which is located on the X chromosome inward band q 27.3, which is nearly at the finish of the long arm. The deoxyribonucleic acid of this cistron codes for a part of the FMRP protein, which plays an significant role inward the brains. Indicates deoxyribonucleic acid that code past times times way of the sequence of 4 chemical amount substances, A, G, C together with T, which deed as letters inward an alphabet. Sets of three-letter code, each quaternary dimension for a exceptional amino acid, 1 of the building blocks of a protein, which is hence constructed according to the code of the DNA. When the fragile-X syndrome, inwards that location is a alter (mutation) formed inward the deoxyribonucleic acid of the FMR1 gene; The "letter" CGG copied endlessly together with is to a greater extent than than 230 times inward a row for (more than 230 "repeats"). As a result, the cistron strength out no longer role together with acts on the disorder. The normal cistron contains between half dozen together with 55 "CGG -repeats". When inwards that location is between the l together with the 200 "CGG-repeats" are (an "premutation"), the cistron strength out nevertheless function, only as the lay out of repeats inward the formation of increasing the egg cell, the mutation is transmitted together with enters the syndrome inward the side past times side generation on. When the FMR1 cistron is not functioning, inwards that location testament alive a shortage of the FMR1-protein, the poly peptide for which it encodes. The absence of this poly peptide seems to atomic publish 82 to nerve cells react strongly to sure transmitters, specially glutamate. This testament relate to the dendritisiche spurs are abnormal inward the fragile X syndrome.
Heredity
Women have got ii X chromosomes inward every cell, males only 1 (and a Y chromosome). Among women inward most cells 1 of the ii X chromosomes made inactive. As a result, inward the half of the cells a "healthy" X-chromosome active. Women with fragile X hence to a greater extent than oft than not have got a much less severe disabilities than men together with strength out oft alive a good for you lot lot carrier. Men strength out the damaged X chromosome only inherit from their adult woman raise (their manly individual raise they inherit the Y chromosome). The designing of good for you lot lot carriers, which have got affected children, called "gender" or "X-linked" inheritance. However, the arrangement from the 1 pictured hither is not entirely because many carriers of fragile X or disabled. A premutation is not associated with an intellectual disability together with generations strength out alive innovate inward a venture unit of measurement of mensuration without going into a mutation. The transition to a mutation of to a greater extent than than 230 repeats occurs only with transmission past times times a woman, who together with too then himself too then no symptoms at all.
Fragile x syndrome symptoms
- Abnormalities inward the human face upward (relatively long face, large ears, prominent chin).
- Macro-orchidie (too large testes)
- Mild to severe mental disabilities; (in women commonly mild, with men commonly severe).
- Shy behavior, avoiding eye contact; This is called autistic.
- Flapping hands inward excitement or stress;
- Language together with spoken linguistic communication disorders; For example, fast talking, oft repeating the '' ain '' words, sometimes incoherent talk.
- Cover Affordability of limbs; depression muscle tone.
- ADHD-like behaviors amidst men with fragile X often;
- In women sometimes come upward upward to depression.
Diagnosis
The diagnosis of fragile X syndrome is suspected inward people with intellectual disabilities together with characteristics. But even out if the typical features are lacking, testament men or boys with intellectual disabilities, whose crusade is unknown, though alive deployed apace investigate the fragile X syndrome. In the deoxyribonucleic acid of the lymphocytes from a blood sample looks at the extension of the cistron that occurs when the lay out of repeats is increased. Can hence alive determined whether the mutation is present. This enquiry may also bring identify inward amniotic fluid or placental villi.
