A reading frame specifies how consecutive nucleotides are grouped into codons. Starting at position 1 of AUGGCUUAA gives AUG / GCU / UAA; starting at position 2 gives UGG / CUU with AA left over. The letters are unchanged but the groups differ. A possible grouping alone does not establish an actual biological translation initiation site.
A reading frame is a way to divide a sequence of nucleotides in DNA or RNA into consecutive, non-overlapping triplets, known as codons. The reading frame determines how the sequence is translated into amino acids during protein synthesis. Because the genetic code is read in sets of three nucleotides, a shift in the reading frame can lead to completely different translations of the same nucleotide sequence.
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