Biology / Unit 6 Bio 1307 short lesson, about 20 seconds
Trinucleotide Repeat Expansions
Captions available
The idea
A trinucleotide repeat expansion increases the copies of a three-nucleotide sequence repeated near a gene, past its normal range.
In practice
A gene's short run of repeated CAG codons can expand across generations into a much longer repeated stretch.
Where people slip
A repeat expansion changes copy number of an existing sequence — it is a distinct mutation type from the substitutions and frameshifts covered earlier.
Your place on the trail
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