What genetic mechanism causes DM1?

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Multiple Choice

What genetic mechanism causes DM1?

Explanation:
DM1 is caused by a CTG trinucleotide repeat expansion in the DMPK gene. When the number of CTG repeats becomes large, the transcribed RNA contains long CUG repeats that act as a toxic RNA, sequestering splicing factors and causing mis-splicing of many transcripts. This RNA gain-of-function effect leads to the muscle weakness, myotonia, and multisystem features seen in DM1 and explains inheritance with anticipation. In contrast, a point mutation would change a single amino acid, a deletion would remove part of the gene, and a duplication would alter gene dosage—none of which produce the toxic RNA–driven mis-splicing characteristic of DM1.

DM1 is caused by a CTG trinucleotide repeat expansion in the DMPK gene. When the number of CTG repeats becomes large, the transcribed RNA contains long CUG repeats that act as a toxic RNA, sequestering splicing factors and causing mis-splicing of many transcripts. This RNA gain-of-function effect leads to the muscle weakness, myotonia, and multisystem features seen in DM1 and explains inheritance with anticipation. In contrast, a point mutation would change a single amino acid, a deletion would remove part of the gene, and a duplication would alter gene dosage—none of which produce the toxic RNA–driven mis-splicing characteristic of DM1.

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