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Molecular cloning is the procedure of making various duplicates of a specific DNA sequence that is utilized to amplify DNA fragments that contain whole genes. It is widely used in biological experiments and practical applications that range from genetic fingerprinting to protein production. Cloning of any DNA fragment mainly includes four major steps:
- Fragmentation is a process of breaking apart a strand DNA.
- Ligation is to glue together the pieces of DNA in a sequence that is desired.
- Transformation which means to insert the recently formed pieces of DNA into cells.
- Screening or Selection which is to select out the cells that were successfully transformed with new DNA.
Initially the DNA should be isolated in order to supply a DNA segment of appropriate size. Afterwards, a ligation procedure is utilized to insert the amplified fragment into a vector or in other words piece of DNA. After ligation the vector is transferred into cells and finally the transferred cells are cultivated. The advanced cloning vectors include antibiotic resistance markers that allows only the cell that the vector was transferred to grow. Nevertheless these selection steps do not guarantee that the DNA insert was fruitful. Further investigation is required to confirm that the cloning was successful. (Peter) SCNT or Somatic cell nuclear transfer is utilized in the production of embryos for therapeutic or research intensions and to create embryos for stem cell researches that is known as Research Cloning or Therapeutic Cloning. This process goal is not to produce cloned human beings but to harvest stem cells which can be utilized to study potentially harmful diseases and the development of human beings. Although a human cloned blastocyst has been produced but stem cell liners are isolated from a cloning source. (Douglas)
Organism cloning is the process of creating a new multicellular organism that is genetically identical to another where there is no fertilization or inter-gamete contact that is referred to as an asexual method of reproduction. Scientists have made great achievements in cloning especially the asexual reproduction of cows and sheep. To create these animals they transfer a nucleus to an egg that has no nucleus from an adult donor cell. Then the egg is transferred into the uterus of a mother if the egg divides normally. Such clones might not be identical since there might be mutation in their DNA of the cell. Another method of cloning is the embryo twinning where an embryo is divided when matured before it is transferred to the embryo. If fruitful then twins are born. The first mammal that was cloned successfully is Dolly the sheep. Although she lived for only six years from 1996 to 2003 but Dolly's cloning was significant since it manifested that the genetic material from an adult cell can be used to create a distinct organism. So far other organisms like tadpole, mouse, dog, camel, and horse were cloned but unfortunately lived for only a short period and then died thus the researches in this field is still ongoing.
The most prominent part of cloning is human cloning that is the process of creating a genetically identical copy of existing or preexisting human beings. There two usual types of human cloning that is reproductive and therapeutic cloning. While therapeutic cloning is the cloning of adult cells for use in researches and medicines reproductive cloning includes making cloned human beings. The third type of cloning is known as replacement cloning, which is a union of therapeutic and reproductive cloning is theoretically possible. It involves replacing damaged or failing body through cloning and it is followed by a partial or whole brain transplant.
When there is a new medicine discovery there are concerns about it short and long term effects for the reason that there can be unprecedented outcome that might not be at all worthy of a try. Always new discoveries were controversial and the cloning of human beings is one of them. As a result of this there have been numerous pleas for all the advancement in human cloning field to be halted. Therefore most religious, scientific and governmental organizations are against human reproductive cloning and request it to be banned until safety issues are taken care of. Although some believe that the human reproductive cloning is an act of copying god in terms of his best creation but others are considering the fact of growing organs separately from a human in order to supply a new organ without harvesting it from humans. There are further researches on xneotransplantation, a process of growing organs inside of other organisms that are biologically suitable to the human body such as cows and sheep and finally transplanting the to humans.
The first human hybrid human clone, produced from an egg of a cow whose DNA was removed and a man's leg, was created by American Cell Technologies, but it was demolished after 12 days. The embryo may have given rise to a complete human being had it been allowed to live but the organization stated that there aim was not “reproductive cloning” but “therapeutic cloning.”
- Peter J. Russell (2005). iGenetics: A Molecular Approach.
- McFarland, Douglas (2000). "Preparation of pure cell cultures by cloning". Methods in Cell Science 22