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Achondroplasia Essay

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Achondroplasia (ACH) is the most common form of short-limb dwarfism occuring in 1 in 15,000 to 28,000 births and appears to be slightly more prevalent in females, but indiscriminent toward race (1-3). Evidence has been found in Egypt for cases of ACH dating back as far as 4500 B.C. (4). In simplest terms, ACH is a disease where the dwarfing of bones formed in the cartilage occurs (5). There are many features that accompany this disease including rhizomelic (proximal) shortening of the extremities, megalencephaly (enlarged brain), short stature, trident hand, and frontal bossing (prominent forehead) (1, 3, 4, 6-8). Expression of this gene at high levels is primarily found in cells of the nervous system and the cartilage rudiments and …show more content…

A point mutation is one where only one nucleotide is changed and a missense mutation is when the amino acid changes due to the base(s) mutated. FGFR3 consists of 19 exons, with the mutation occuring in exon 10 (1, 16). Furthermore, the mutated base is 1138, where the base can undergo two possible mutations. G(guanine)→A(adenine) transition accounts for 98% of all cases of ACH while the G→C(cytosine) transversion mutation occurs in 1% of cases (6). Both of these mutations result in the amino acid arginine being substituted for glycine at codon 380 which is in the transmembrane of FGFR3 (1, 4, 17) (See Figure 1). The FGFR3 mutation is a gain-of function mutation due to the resulting activation of receptors, which is opposite the normal inhibitory effect the FGFR3 has on the receptors, which upon activation, negatively regulate bone growth (4, 6). Thus, FGFR3 has been found to become hyperactivated when mutated and undergo ligand-independent dimerization (1, 11, 18). De novo mutations account for 80-90% of all cases of ACH (1, 4, 7, 8, 11). Recent research has determined that increased paternal age correlates to this specific mutation occuring (4, 7, 11, 19). The maternal age seems to have no effect, meaning that the de novo mutation occurs during spermatogenesis (20). This has also been studied and each affected individual was found to have received the mutated chromosome paternally (21). There has only been one documented case of an

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