What is Cloning? 2097605583.jpg



Cloning is the creation of an orgainism that is the exact genetic copy of another. This includes the same DNA, leading to the same fingerprints, blood type, genetic abilities etc. However, cloning does not always occur in labs, as there are natural cases of cloning: twins. However, these "clones" still have big differences, and are not "true" clones.

Twins are the result of a fluke in nature. After a sperm has fertilized an egg, the cell may split, forming two human beings, using the exact same set of 23 chromosomes from each parent. They are "genetically" exact copies of each other.
Read about an interesting cases in point here!


How is Cloning Done?


Dolly the Sheep external image dolly_80.jpg


Dolly the sheep was the first organism to be fully cloned in a lab, dispite the fact that cloning technology was developed long before Dolly was successfully cloned. However, at six years old, Dolly suffered progressive lung diesease and was eventually "put to sleep." This example made researchers hesitant about cloning in the future.

The Process of Cloning

The first method of cloning is called artificial embryo twinning. This process is a low-tech version of cloning and mimics that natural occuring event of indentical twins.


Different types of cloning


1. Recombinant DNA technology or DNA cloning:
See the Gene Splicing page

2. Reproductive Cloning
The technology used to create an animal that has the same nuclear DNA as the original animal that it is cloned from. Genetic material from the nucleus in the same of the origin is moved to a egg with a nucleus emptied of its original genetic material; this process is known as the ‘somatic cell nuclear transfer’. The newly created egg cell needs chemicals and electric currents for it to start dividing. When the embryo is developed to a certain degree, it is transferred into a uterus of a female host.

Dolly is an example of reproductive cloning.

3. Therapeutic Cloning

Therapeutic cloning is also known as "embryo cloning." This is because it deals with the production of human embryos. The ultimate goal is not to create a new, whole human being, but to harvest stem cells in order for scientists to research diseases and human development. Stem cells can be used to create (potentially) virtually any cell in the human body. Researchers hope one day to use these stem cells to create replacement cells for humans, in order to treat various diseases or for organ transplants.

More information on all three types of cloning can be found here.


Identical Copies?


Theoretically, cloning an organism means that the end product will be two identical organisms, right down to the last nitrogen base. However, in practice this is usually not the case. Oftentimes there are differences between the original organism and the clone. For example, it has been noted that Dolly the sheep had slightly shorter chromosomes than other sheep.

And of course, even scientists cannot know if a clone will take on the same personality traits (or, as people of religion would put it, the "soul") as the original. This is the classic question of nature versus nurture.



Risks of Cloning



1. High chance of failure
Cloning by somatic cell nuclear transfer only has 0.1% to 3% success:
- the original egg cell and the nucleus being transferred may not be compatible
- division and development may fail
- implantation of the created embryo into a surrogate mother may fail
- pregnancy may fail

2. Possible problems during later development
Many cloned animals tend to be relatively larger at birth compared to natural animals. This is also known as the Large Offspring
Syndrome (LOS). Even those that are not diagnosed with LOS have high chances of physical abnormalities such as kidney or brain malformations and failed immune systems; all of these factors will hinder normal development later in life.

3. Abnormal gene expression patterns
Embryos in natural animals have DNA that are specifically taught or programmed to express certain genes. Each cells later begin to adopt their unique characteristics and experience what is known as 'differentiation'. Once they are differentiated, their program for gene expression changes. However, as the cloned embryos are not able to do this, they are likely to present abnormal gene expressions if not reprogrammed.

4. Telomeric differences
When cells go through numerous divisions, the length of their chromosomes tend to become shorter as the end DNA sequences, the telomeres, shrink when the DNA is copied. Therefore, the older the cell, the shorter its chromosomes will be. However, some cloned animals proved to have longer telomeres compared to those of naturally born animals. Nevertheless, Dolly the sheep displayed shorter chromosomes. To this day, scientists have not been able to clarify why these telomeric differences appear in cloned animals.

visit the source here




Ethical Concerns



As cloning technology has progressed, concerns have been expressed about the ethicality of cloning. Such concerns can usually be broken down into two categories: Religious arguments and ethical arguments.

Religious arguments vary from religion to religion. Usually the problem is that it is against a particular religion for humans to "play God," per se. For example, Roman Catholics strongly believe that birth is an act of God, and that the baby is created in the image of God. When humans clone, they are duplicating an already "made" human, instead of reflecting God's wishes. Many Christians who believe in the concept of a unique soul for every person wonder if cloning can also duplicate the elusive soul along with the actual body. Some Muslims worry that cloning conflicts with the very important Islamic idea of kinship: Clones do not have actual "parents."

Ethical arguments center around the question of how much a human life is worth. Cloning potentially devalues each life, since efficient cloning would lead to organisms' easily being manipulated. Those who endorse the ethical argument argue that cloning degrades both the family as a whole as well as each person's personal sense of worth and independence. Then there are those who put forth the economic problem of scarce resources--why put time and money into cloning research when no cures for greater problems such as AIDs or cancer have been discovered?

When dealing with just animal clonings, many people still voice ethical concerns. Animal cloning is thus far less complicated than human cloning (which has yet to be fully realized), but it is important to remember that each success in animal cloning was preceded by countless laboratory failures. And even the ones that succeed end tragically, such as Dolly's story above. The same moral concerns applied to humans can definitely be applied to animals, since they too feel pain. Can we humans humanely subject animals to numerous tests and experiments without knowing exactly what the result will be?

As with any revolutionary idea, cloning is experiencing backlash from human beings who are naturally uncomfortable with drastic changes. In the future, governments and scientists will have to carefully measure the benefits of cloning with the possible repurcussions of it.

sources for this section: http://www.cs.virginia.edu/~jones/tmp352/projects98/group1/ethic.html
http://www.rds-online.org.uk/pages/page.asp?i_ToolbarID=5&i_PageID=162

Gene Cloning

Gene cloning is a process by which large quantities of a specific, desired gene or section of DNA may be cloned or copied once the desired DNA has been isolated.

Method of Gene Cloning:

1) Using restriction enzymes, which have ability to cut DNA molecules at certain size.2) Treating desired gene and a plasmid by using the same restriction enzyme in order to make identical ends.

3. Using DNA ligase to splice the DNAs.

4. Using recombinant DNA and plasmid which contains the added DNA.

5. By using the process called transformation

6. As the bacterial cells reproduces (by mitosis), the recombinant plasmid is copied. Soon, there will be millions of bacteria containing the recombinant plasmid with its introduced gene. 7. The introduced gene can begin producing its protein via transcription and translation.

external image recombinant.gif

http://ghs.gresham.k12.or.us/science/ps/sci/
Example of Gene cloning
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ibbio/biotech/genecloning.htm