The origin of replication is a sequence of DNA capable of directing the spread of itself and any linked sequence. However, a certain number of other features are needed along with a variety of specialised cloning vectors, which allow protein expression, tagging, single stranded DNA or RNA production, and various other manipulations. 1, 2
Molecular cloning using any kind of DNA fragment is essentially done in four steps: Fragmentation, ligation, transfection, and selection. Although these are the basic steps there are some alternative routes. 1, 2
Example of DNA fragmentation Pg4
http://www.mmi.mcgill.ca/mmimediasampler2002/images/beauchemin-15no11firstframe.gif
Cellular cloning
Cellular cloning is when you develop a population of cells from a single cell. For unicellular organisms (yeast, bacteria) cellular cloning is fairly simple. But for multi-cellular organisms (animals, insects) it is a much harder task, as the cells will not grow readily in the standard medium.
A useful tissue culture technique used to clone distinct lineages of cell lines involves the use of cloning rings. According to this technique, a single-cell suspension of cells which have been exposed to a or drug used to drive is plated at high dilution to create isolated colonies; each arising from a single and potentially clonally distinct cell. At an early growth stage when colonies consist of only a few of cells, sterile rings (cloning rings), which have been dipped in grease, are placed over an individual colony and a small amount of is added. Cloned cells are collected from inside the ring and transferred to a new vessel for further growth. 1, 2
Cellular cloning using rings
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Organism cloning & Somatic cell nuclear transfer
Organism cloning or asexual reproduction is the process of making an identical copy of a multi-cellular organism. Asexual reproduction means that no fertilization is being made, and that only one parent is actually being used.
There is also somatic cell nuclear transfer, which is used to create a clone of an embryo mainly for stem cell research. Somatic cell nuclear transfer is when you create an ovum using a donor nucleus. Somatic cell nuclear transfer research can also be used in the first step of the cloning process. 5, 1, 3, 2
Example of nuclear transfer.
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Dolly the sheep
In 1996 Dolly the sheep was the first successful mammal to be cloned from an adult cell. The first animal to be cloned ever was a tadpole in 1952.
Dolly was made from three other sheep. The scientists made her by taking the nucleus from an egg cell of one of the sheep and replacing it with the nucleus of an udder cell of another sheep. The egg cell was then put into the uterus of another sheep. Dolly is an exact clone of the sheep that donated the nucleus from its udder cell because that is where the Dolly’s DNA came from.
Cloning Dolly the sheep had a low success rate per fertilized egg; she was born after 277 eggs were used to create 29 embryos, which only produced three lambs at birth, only one of which lived. Seventy calves have been created from 9,000 attempts and one third of them died young.
Dolly the sheep had arthritis young died at the age of six; scientists think that this is because she was a baby calf with the DNA of an adult sheep. 1, 3, 5, 4
The making of Dolly using the other three sheep
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Arguments for cloning
There are any arguments for cloning, such as that it can cure diseases by developing organs to help people with heart problems, or by using stem cell research to make a copy of an embryo. Stem cells have the ability to grow in laboratories and can go into almost all types of bodily tissue. This makes stem cells good for cellular therapies, which is done for treating various diseases. Cloning also enables the reproduction and development of organs, which could be used to replace failing or weak ones.
Cloning could make the ‘perfect’ child by adjusting the DNA in a cell to make it look how someone wants it to look or produce children immune to diseases or imperfections.
It could also be useful in stopping endangered animals from becoming extinct or even using DNA from ancient fossils to bring extinct animals back to life.
Cloning could even genetically modify animals to help people with allergies to their products such as making cows produce milk that does not contain lactose for people that are lactose intolerant or genetically modify fruits and vegetables to make them perfect for eating or to make them so that they do not need pesticides.
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Arguments against cloning
The majority of the arguments against cloning are ethical and some of them have to do with religion.
Many religious people believe that the concept of cloning is just trying to ‘play god’. This means that by cloning, scientists are doing god’s job. Most religions are against it because this questions the concept of the world having been created by a superior force or a god.
Another argument against cloning is that criminals could use cloning to make copies of themselves, so that the clones would get arrested instead of them if the police were chasing them. People could also develop armies of clones to fight wars.
People predict that cloning could generate a black market for stolen or discarded embryos.
There are also some practical issues about cloning such as the misuse of life. For example, it took hundreds of attempts to make Dolly the sheep.
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Conclusion
In conclusion, I think that although roughly the same amount of arguments for and against cloning was presented in this case study; I am more persuaded that cloning should be allowed. This is because I believe that there are more benefits to be gained from cloning in comparison to the harm it could cause. For instance, consider the advantages cloning processes such as therapeutic cloning could bring to the welfare of humans? However, I think that there should be legal limits to control the abuse of cloning such as the production of an entire human being.
Though I believe that cloning is useful, I have considered the alternative and have found that many of the arguments against (especially the ones to do with religion) are not relevant when compared to the fact that human lives could be save.
But besides religion, I have also considered the other arguments against cloning such as the number of egg cells used as part of the process. Potentially millions of patients could benefit from stem cell therapy, but patients would require a large number of donated eggs in order to successfully create a single custom therapeutic stem cell line.
Cloning is a new technique that needs to be developed in practise since a lot of the assumptions made about the benefits of cloning are only in theory.
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Bibliography
All of the information that I used on pages 3-7 was from 1 1)
2)
3)
4)http://www.brainpop.com/science/cellularlifeandgenetics/dollythesheep/
5) http://www.ornl.gov/sci/techresources/Human_Genome/elsi/cloning.shtml#intro
Arguments for cloning taken from
www.questacon.edu.au/html/arguments_for_cloning.html
Arguments against cloning taken from www.questacon.edu.au/html/arguments_against_cloning.html www.allaboutpopularissues.org/arguments-against-cloning-faq.htm
When it comes to the scientific information, I think that and are both more reliable than because we know that in the science museum and in brainpop all this has been properly researched and tested, because the science museum is a museum and brainpop is a website to help out teachers, and in www.wikipedia.org someone could have been making some stuff up. And for the arguments, I believe that wikipedia is a lot more reliable than because all about popular issues was a religious page that kept advertising Jesus.
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