Question

Three human disorders−−fragile X syndrome, myotonic dystrophy, and Huntington's disease−−are conceptually linked by a common mode of molecular upset. Choose the phenomenon that links these disorders. Three human disordersfragile X syndrome, myotonic dystrophy, and Huntington's diseaseare conceptually linked by a common mode of molecular upset. Choose the phenomenon that links these disorders. All three are caused by disparate genes, but each gene was found to contain repeats of the same trinucleotide sequence. All three are X-linked, but each gene was found to contain repeats of the same trinucleotide sequence. All three are caused by disparate genes, but each gene was found to contain repeats of a unique trinucleotide sequence. All three are X-linked, but each gene was found to contain repeats of a unique trinucleotide sequence.

Answer 1

Answer:

The correct answer is ''All three are caused by disparate genes, but each gene was found to contain repeats of a unique trinucleotide sequence.''

Explanation:

Four groups of trinucleotide repeats related to DNA expansion have been characterized in the human genome. CGGI GCC, CAGIGTC, CTGIGAC and recently GW CTT sequences. The CGGl GCC sequences are usually located in the noncoding regions of different genes and when expanded they associate with fragile sites on the chromosomes. The CAGIGTC repeats are part of the coding region and are related to different neurodegenerative disorders. You can try to make a classification depending on the unit that is repeated, having on one side a group that are caused by repeats of the CAG trinucleotide (cytosine, adenine, guanine). Huntington's disease (HD) is a progressive disorder of motor, cognitive and psychic function. The disease is inherited in an autosomal dominant manner, and is caused by the expansion of CAG trinucleotide repeats in exon 1 of the gene called huntingtin (HTT or IT-15). Unstable mutations have also been found in which the repeat unit does not is composed of three nucleotides, if not four, such as type 2 myotonic dystrophy, where the tetranucleotide CCTG repeats. Fragile X Syndrome consists of an abnormal expansion of the cytosine-guanine-guanine trinucleotide (CGG) in the FMR1 gene, which prevents intellectual disability and also influences the formation of connective tissue