Classification Overlapping gene

tandem out-of-phase overlap of human mitochondrial genes atp8 (+1 frame, in red) , atp6 (+3 frame, in blue)

genes may overlap in variety of ways , can classified positions relative each other.

unidirectional or tandem overlap: 3 end of 1 gene overlaps 5 end of gene on same strand. arrangement can symbolized notation → → arrows indicate reading frame start end.
convergent or end-on overlap: 3 ends of 2 genes overlap on opposite strands. can written → ←.
divergent or tail-on overlap: 5 ends of 2 genes overlap on opposite strands. can written ← →.

overlapping genes can classified phases, describe relative reading frames:

in-phase overlap occurs when shared sequences use same reading frame. known phase 0 . unidirectional genes phase 0 overlap not considered distinct genes, rather alternative start sites of same gene.
out-of-phase overlaps occurs when shared sequences use different reading frames. can occur in phase 1 or phase 2 , depending on whether reading frames offset 1 or 2 nucleotides. because codon 3 nucleotides long, offset of 3 nucleotides in-phase, phase 0 frame.




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