Most disorders attributable to trinucleotide repeats result from expansion of th

Question

Most disorders attributable to trinucleotide repeats result from expansion of the repeats. Two mechanisms are often proposed to explain repeat expansion. (1) unequal synapsis and crossing over and (2) errors in DNA replication where single-stranded, base-paired loops are formed that conflict with linear replication. Notice that some of the repeats occur in areas of the gene that are not translated. How can a mutation occur if the alteration is not reflected in an altered amino acid sequence? Select all that apply. a. Repeats often activate attraction in the coding regions of genes. Attraction may distort the spicing process or may change the direction of motion of regulatory signals b. Repeats often change the genes so that normal function of the gene is occupied or interrupted. Without functioning genes do not have enough sources to translate normally. c. Repeats that occur outside of the coding regions do not have an effect on the gene product. There are other factors that contribute to the onset of these disorders. d. Repeats within introns may upset the spiking process or may actually Influence regulatory sequences that are contained In introns. e. Repeats often upset regulatory signals both upstream and downstream from the coding regions of genes.

Explanation / Answer

Answer is b. and e

It was suggested that repeats that multiple of three are not viable. Trinucleatide repeats that present near to coding sequence are prone for repeat expansion and repeats that are multiple of three can cause framshift mutations. The most common expansion is reported is CAG trinucleotide expansion. This can affect both regulatory sequence of upstream and downstream.

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