What is Cloning ?

Cloning is the creation of an organism that is an exact genetic copy of another. This means

that every single bit of DNA is the same between the two!

How is cloning done?

• You may have first heard of cloning when Dolly the Sheep showed up on the scene in 1997. Cloning technologies have been around for much longer than Dolly, though

How does SCNT differ from the natural way of making an embryo?

• The fertilization of an egg by a sperm and the SCNT cloning method both result in the same thing: a dividing ball of cells, called an embryo

CLICK AND CLONE

• 1: Isolate donor cells from Mimi and Megdo• 2: Remove & discard nucleus from egg cell• 3: Transfer somatic cell nucleus into enucleated

egg cell• 4: Stimulate cell division• 5: Implant into embryo into Mimi, surrogate

mother• 6: Deliver baby mouse clone of Mimi

The Clone Zone

• 1885: See Double ? Sea Urchins Cloned

• 1902: Slimy Salamanders Cloned

• 1968: Cloning, Any Nucleus Will Do

• 1996: Hello, Dolly!

• 1997: Following Dolly, Pharming Polly

• 2002: House Supports Cloning Ban

WHY CLONE?• . Cloning for medical purposes• • Of all the reasons, cloning for medical purposes has the most potential to

benefit large numbers of people. How might cloning be used in medicine?•

• Cloning animal models of disease

• Much of what researchers learn about human disease comes from studying animal models such as mice. Often, animal models are genetically engineered to carry disease-causing mutations in their genes. Creating these transgenic animals is a time-intensive process that requires trial-and-error and several generations of breeding. Cloning technologies might reduce the time needed to make a transgenic animal model, and the result would be a population of genetically identical animals for study.

Reviving Endangered or Extinct Species

• Have you seen Jurassic Park? In this feature film, scientists use DNA preserved for tens of millions of years to clone dinosaurs. They find trouble, however, when they realize that the cloned creatures are smarter and fiercer than expected.

• Could we really clone dinosaurs?• In theory? Yes. What would you need to do this?• A well-preserved source of DNA from the extinct dinosaur, and • A closely related species, currently living, that could serve as a

surrogate mother• In reality? Probably not. It's not likely that dinosaur DNA could

survive undamaged for such a long time. However, scientists have tried to clone species that became extinct more recently, using DNA from well-preserved tissue samples. For an example, see "Can we really clone endangered or extinct animals?" on the right side of this page.

Reproducing a Deceased Pet

• No joke! If you really wanted to, and if you had enough money, you could clone your beloved family cat. At least one biotechnology company in the United States offers cat cloning services for the privileged and bereaved, and they are now working to clone dogs. But don't assume that your cloned kitty will be exactly the same as the one you know and love.

CLONING MYTHS

• Misconception #1: Instant Clones! A common misconception is that a clone, if created, would magically appear at the same age as the original. This simply isn't true. You remember that cloning is an alternative way to create an embryo, not a full-grown individual. Therefore, that embryo, once created, must develop exactly the same way as would an embryo created by fertilizing an egg cell with a sperm cell. This will require a surrogate mother and ample time for the cloned embryo to grow and fully develop into an individual

Misconception #2: Carbon Copies!

• Your beloved cat Frank has been a loyal companion for years. Recently, though, Frank is showing signs of old age, and you realize that your friend's days are numbered. You can't bear the thought of living without her, so you contact a biotechnology company that advertises pet cloning services. For a fee, this company will clone Frank using DNA from a sample of her somatic cells. You're thrilled: you'll soon have a carbon copy of Frank - we'll call her Frank #2 - and you'll never have to live without your pal! Right?

• Not exactly. Are you familiar with the phrase "nature versus nurture?" Basically, this means that while genetics can help determine traits, environmental influences have a considerable impact on shaping an individual's physical appearance and personality. For example, do you know any identical twins? They are genetically the same

WHAT ARE THE RISKS OF CLONING?

• 1. High failure rate• Cloning animals through somatic cell

nuclear transfer is simply inefficient. The success rate ranges from 0.1 percent to 3 percent, which means that for every 1000 tries, only one to 30 clones are made. Or you can look at it as 970 to 999 failures in 1000 tries. That's a lot of effort with only a speck of a return

• 2. Problems during later development

• Cloned animals that do survive tend to be much bigger at birth than their natural counterparts. Scientists call this "Large Offspring Syndrome" (LOS). Clones with LOS have abnormally large organs. This can lead to breathing, blood flow and other problems.

• 3. Abnormal gene expression patterns• Are the surviving clones really clones? The

clones look like the originals, and their DNA sequences are identical. But will the clone express the right genes at the right time?

• In Click and Clone, we saw that one challenge is to re-program the transferred nucleus to behave as though it belongs in a very early embryonic cell. This mimics natural development, which starts when a sperm fertilizes an egg

• 4. Telomeric differences

• As cells divide, their chromosomes get shorter. This is because the DNA sequences at both ends of a chromosome, called telomeres, shrink in length every time the DNA is copied.