Kinds of Typos in DNA
Take the reading one piece at a time. For each piece: read it once, underline the sentence that says what happens, then look up any word in the list. Tap a word to see its definition.
Piece 1 of 2
DNA is read three letters at a time, and each three-letter word (a codon) either names one amino acid or says stop. Read this sentence three letters at a time, the way a ribosome reads mRNA: THE BIG RED DOG RAN FAR (each word is one amino acid). Edit 1 changes one letter so RED becomes a different word of the same length (a missense). Edit 2 turns DOG into a STOP word, so the reader stops and everything after is lost (a nonsense). Edit 3 deletes one letter, so every word after the deletion is re-grouped wrong and the rest is gibberish (a frameshift). Edit 4 lands exactly at the seam where two pieces are spliced together, so the wrong pieces get joined (a splice-site change).
Piece 2 of 2
Real IRF6 variants sort into these same categories. R84C changes amino acid 84 from arginine (R) to cysteine (C): missense, full-length protein, possibly broken. R250X turns codon 250 into a STOP (the X): nonsense, protein cut short at position 250. An insertion or deletion not a multiple of 3 is a frameshift, scrambling everything downstream and usually ending in an early stop. A change at an intron/exon boundary is a splice-site variant. Reading the code: a letter, a number, a letter (R84C) means missense; a letter, a number, then X (R250X) means nonsense.
Reading the Research
- Skim the title and abstract first to get the gist.
- Circle the one sentence that states the main claim.
- Box the evidence the authors give for that claim.
- Mark one sentence that confuses you, and move on.
Now put it together: In one or two sentences, say what this whole reading is telling you about Mateo. Then go back to the lesson and fill in the guided notes.