gene search then and now.

1866 Experimenting with plants, Austrian botanist and monk Gregor Mendel shows how characteristics are inherited and proposes basic laws of heredity.

1944 The work of biologists Oswald Avery, Colin MacLeod, and Maclyn McCarty on the pneumococcus bacteria proves that DNA is the hereditary material in most living organisms.

1953 Biochemists James Watson and Francis Crick discover that the DNA molecule has a double-helix structure.

1973 By transferring a gene from an African clawed toad into the DNA of a bacteria, biochemists Stanley Cohen and Herbert Boyer pioneer genetic engineering.

1983 To speed up the process of reproducing tiny bits of DNA, biochemist Kary Mullis develops a technique called polymerase chain reaction.

1990 The international Human Genome Project begins. Its goal: to map and sequence all of human DNA by 2005.

1995 For the first time, scientists decode the entire DNA sequence of an organism: a bacteria known as Hemophilus influenzae.

1997 Researchers at the Roslin Institute in Scotland done Dolly the sheep from the DNA of an adult sheep.

1998 Biologist J. Craig Venter announces that his company will decode the human genome by 2001. Officials from the Human Genome Project promise to have a "rough draft" by the same year, and a complete map by 2003.

1998 scientists decipher the genome of the first multicellular organism--a roundworm known as Caenorhabditis elegans.