The two stamps you describe are part of a set of 5 issued in February to commemorate the 50th anniversary of Crick and Watson uncovering the double helix structure of DNA. They announced their discovery "We have discovered the secret of life" in The Eagle pub in Cambridge, England.

The stamps present five cartoon representations of key areas in genome research.

2nd Class: The End of the Beginning - The piece of the jigsaw puzzle signifies that the discoveries made so far, and the mapping that continues, present us with the method of finding the beginning of life.

1st Class: Comparative Genetics - Highlights the fact that 95-98% of the genes in humans and apes are the same.

E Class: Cracking the Code - The twisted ladder with a snake signifying that DNA is a double-helix, but also that the process can sometimes be ‘one step forward and two back’.

47p: Genetic Engineering: The mix and match of genes from different organisms and how genes can be transferred from one species to make another.

68p: Medical Futures: The immense possibilities arising from the mapping, sequencing and analysis of the human genome are viewed through a scientific crystal ball.

For those of a technical turn of mind, the details of the stamps are:
Designer: Williams Murray Hamm
Illustrator: Peter Brookes
Stamp Format: Horizontal
Stamp Size: 37mm (w) x 35 (h) mm
Printer: Joh Enschedé Security Print
Print Process: Litho
Number per Sheet: 50
Perforations: 14 x 14.5
Phosphor: As appropriate
Gum: PVA