What hypothesis did Levine propose?

Levine proposed the tetranucleotide hypothesis, which suggests that nucleic acids are composed of repeated units of four nucleotides, specifically the four nucleotide bases that make up DNA and RNA. This idea was instrumental in advancing the understanding of DNA structure and function during its time, as it laid the groundwork for the recognition that the information carried by DNA is encoded in the sequence of these nucleotide units.

This hypothesis was significant because it challenged previous notions regarding the complexity and variability of genetic material, suggesting instead that this complexity could stem from variations in the sequencing and arrangement of a limited number of nucleotides. The tetranucleotide hypothesis eventually led to more robust models of DNA and its function in genetics, though it was later revised as understanding of DNA structure improved.

In contrast, the other options represent different important ideas in genetics that were proposed by various researchers, but they do not directly relate to Levine's contributions.