Chad Clark's Open Journal : 2010-02-17

1) Cells that can express 4-letter codons.

Popsci is reporting people have created infrastructure to support 4 letter codons.

  RNA can only read three-letter combinations. Called codons, these three
  DNA-base-pair groups form the phrases that RNA translates into the 21
  amino acids that underlie all life. But now, University of Cambridge
  researcher Jason Chin has engineered more literate RNA, capable of
  reading codons composed of four base pairs. This expands the possible
  number of codons from 64 to 320
  
  ...
  
  By expanding the vocabulary of DNA, Li and his team also expand the range
  of possible compounds a cell could produce.