Final answer:
Overlapping genes are true and do exist, especially in the viral genomes, allowing for a more compact and efficient use of genetic material. In most organisms, the genetic code is non-overlapping, allowing a greater diversity of protein sequences.
Step-by-step explanation:
The statement that occasionally overlapping genes/open reading frames are found is A. True. In genetic coding, overlapping genes are a phenomenon where a single nucleotide sequence encodes for two or more proteins. This can happen when a single strand of DNA contains multiple open reading frames (ORFs), and these frames may overlap, allowing for different proteins to be produced depending on where translation begins. Although the genetic code is typically non-overlapping, as each set of three nucleotides (codon) codes for only one amino acid, there are exceptions, particularly in viral genomes. For example, the ΦX174 bacteriophage's genome has specific genes that overlap, such as Gene B being within Gene A's sequence, and Gene E overlapping with Gene D. This packing of genetic information allows viruses to maximize the use of their small genomes.
However, in higher organisms, overlapping genes are less common. The genetic code does not generally support overlapping codons because this would limit the possible amino acid sequences that proteins could have, as indicated by accumulating amino acid sequences in scientific literature. Therefore, the genetic code is predominantly non-overlapping to allow for the vast diversity of proteins that living organisms require.