MoBio Gene Overlapping Chapter 5

From the phenomenon of frameshift, we see that the same nucleotide sequence could encode different amino acid sequences. This allows two genes with entirely different protein products to share the same nucleotide sequence. The gene overlapping is often found in a compact genome such as HBV and HIV. In human mitochondrial DNA, there are two overlapping genes: ATPase subunits 6 and 8.

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Figure 5-C-3. An example of gene overlapping. The gene of ATPase subunit 8 is located between 8366 and 8569 of the human mitochondrial genome. The gene of ATPase subunit 6 is located between 8527 and 9204. ATPase 8 contains 68 amino acids while ATPase 6 has 226 amino acids. Their amino acid sequences are different even in the region where they share the same DNA sequence. It is interesting to note that the end of the ATPase 6 gene is not a stop codon, but two nucleotides "TA". It becomes the stop codon "TAA" only after the poly-A tail is added during RNA processing!