Cloning: A Historical Overview

Artificial insemination begins: Bull semen is successfully frozen to be used later to inseminate female cows.

A step towards cloning: Robert Briggs and Thomas King tried unsuccess- fully to clone a frog by taking a nucleus from a cell of an advanced frog embryo and adding it to that of a frog egg.

Award-winning discovery: The "double helix" structure of DNA is discovered by British scientists James Watson and Francis Crick, earning them the 1962 Nobel Prize in Physiology.                                                  

A more successful frog: John Gurdon took the nucleus of a frog egg and replaced it with one from a cell of an older frog, thereby cloning a frog.

Steen Willadsen reported that he used immature sheep embryo cells to clone a lamb. Soon this technique is used to clone many other animals.

Another first: A successful human mother-to-mother embryo transfer occurs.

First "test-tube baby," Louise is born: The first child conceived through in vitro fertilization enters the world.

Lab work: The first transgenic livestock, pigs that produce human growth hormones, are created in Ralph Brinster's lab.

Mary Beth Whitehead, an artificially inseminated surrogate mother, carries "Baby M" to full term, and then tries to keep her. She fails.

The Human Genome Project starts to categorize the nature and placement of all the human genes.

Human embryos are successfully cloned.

Cloning technology is used  to create a bull calf named "Gene."

The experiments continue: Ian Wilmut tried a variation on Dr. First's sheep experiment. However, the eggs simply developed into normal embryos and then into normal lambs.

Fruitful mistake: One of Neal First's lab staff accidentally starved an embryo by forgetting to feed it the nourishing semen. The result: four calves were cloned from embryos that had grown to over 120 cells.

More on sheep: The Roslin Institute introduces the first transgenic lambs produced by nuclear transfer.

Aftermath and ethical complications: The issue of human cloning is raised, and debates rage over the ethics of such practices. Meanwhile, world governments (including the U.S. government) attempt to introduce regulations that would make the cloning of humans illegal.

July -  Mice are cloned in Hawaii.