Cloning

Cloning in Animals

Organisms that are genetically identical are clones

Asexual Reproduction always produces clones

Laboratory Techniques have been developed that have allowed this to happen in Animals

Wishful Thinking!!!

Cloning in Plants

Plant Cloning

1950’s first experiments done with Frogs. When Transplanted nuclei from cells of Tadpoles

and Frog Embryos into egg cells that had their nuclei removed(Briggs and King) They found that many of the eggs would develop into tadpoles if the source of the original nucleus was the early embryo. When they took Tadpole nuclei they would not.

Also found that the tadpoles that did arise would not develop into adults

Results gave support to the idea that differentiated cells could not be used to create clones

Impossible becomes Possible

Early 1990’s some success found with MiceMice were cloned by using nuclei of cells

taken from Mice Embryos

Heres Dolly!!!

Wilmut et al. Produced “Dolly” in 1997Used Genetic Information Taken from

Udder of Adult Sheep In order for differentiated cells to be cultured

to produce an undifferentiated embryo the process of Cell Differentiation had to be reversed.

Cloning - Steps

Unfertilized Eggs Collected from a donor sheep and had nuclei removed

From 2nd Animal removed a sample of Udder cells. These Cells were cultured and had cell cycle arrested during the G Phase

Nuclei from Udder Cells Transplanted into the egg cells. Resulting Cells were cultured and a few began to divide. These early embryos implanted into a surrogate mother. One of

these developed into a Lamb – Dolly DNA Tests confirmed that the Lamb was identical Genetically to

the Sheep that had provided the Udder Cells

Problems

Other Researchers have repeated the work but as more examples are created there is evidence that there are health problems associated with the Cloned Animals. Dolly showed signs of Premature Aging.

Human Cloning

Very Controversial TopicDifference Between:

Therapeutic Cloning – Culturing of Human Cells for use in Treating Medical Disorders

Reproductive Cloning – Development of a cloned human embryo for the purpose of creating a cloned Human Being

How is Therapeutic Cloning Done?

Eggs are coaxed to mature in a culture dish. Each has a remnant egg cell called the polar body and cumulus cells from the ovary clinging to it.

While an egg is held still with a pipette, a needle is used to drill through the zona pellucida, removing a plug.

After ejecting the zona plug, the needle is inserted back in the egg through the hole to withdraw and discard the polar body and the egg's genetic material.

A cumulus cell from another egg is taken up into the needle. Cells called fibroblasts (or their nuclei) can also be used in this step.

The cumulus cell is injected deep into the egg that has been stripped of its genetic material.

The injected egg is exposed to a mixture of chemicals and growth factors designed to activate it to divide.

After roughly 24 hours, the activated egg begins dividing. The cells contain genetic material only from the injected cumulus cell.

By the fourth or fifth day, a hollow ball of roughly 100 cells has formed. It holds a clump of cells called the inner cell mass that contains stem cells.

The blastocyst is broken open, and the inner cell mass is grown in a

culture dish to yield stem cells.

The stem cells, in turn, can be coaxed to grow into a variety of cells that might one day be injected into patients.

Controversy

Proponents of Therapeutic Cloning argue that this may provide key to eliminating Disease

Yet all means of cloning does result in the creation and destruction of hundreds of embryos.

Cloning Technologies have the potential to change the definition of life.