Complex sentence: The fact that there are 61 amino-acid-coding codons and only 20 amino acids presented a problem; in 1966 Francis Crick proposed the Wobble hypothesis to account for this.
Split into simpler sentences: The fact that there are 61 amino acid coding codons and only 20 amino acids presented a problem. But in 1966 Francis Crick proposed the Wobble hypothesis to account for this.