How is the reading frame start position in a feature used?
The readingFrameStartPosition defines the position of the first base in the first codon in a coding region on the reference sequence. It is used to determine the amino acid a variant codes for and is therefore only applicable to coding features (i.e. exons). In the sequence below, intronic regions are denoted in lower case and exons are denoted in upper case and the first base (the left-most c) is position 1. Position: 4 27 | | cccGATGATGATGATGccccccccccTATGATGATGaaa If the reading frame begins at position 4 for the first exon and at position 27 for the second exon, then the codons for this sequence would be GAT GAT GAT GAT GTA TGA TGA TG. If, however, the reading frame begins at position 5 for the first exon, then the codons for this sequence would be ..G ATG ATG ATG ATG TAT GAT GAT G.., which would change the amino acid translation of the sequence.
