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Asexual reproduction and cloning

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Introduction

Asexual reproduction. When organisms reproduce asexually, there is no fusion of sex cells. A part of the organism grows and somehow breaks away from the parent organism. The cells it contains were formed by mitosis, so contain exactly the same genes as the parent. A sexual reproduction produces offspring that are genetically identical to the parent, and genetically identical to each other. A sexual reproduction is common in plants. For example, flower bulbs grow and divide asexually each season to produce more bulbs. Asexual reproduction also occurs in some animals such as the Hydra, a small freshwater animal, which reproduces asexually by 'budding'. Artificial cloning Artificial cloning of animals is now commonplace in laboratories. ...read more.

Middle

4. Before the dividing cells became specialised the embryo was implanted into the uterus of a foster-mother sheep. The result was Dolly, genetically identical to the donor sheep. Advantages of embryo transplanting Disadvantages of embryo transplanting Allows screening for defects in gametes Does not add variety - so no opportunity for natural selection Makes it possible to choose sex and time of birth Lack of hybrid vigour - animals potentially vulnerable to disease Exact copies of the 'best' animal specimens, year after year Danger of reducing the gene pool Could be used for saving endangered species from extinction Some animal welfare concerns - e.g. about the longevity of cloned animals Cloning organs. ...read more.

Conclusion

If organs could be generated from cloned human embryos, the need for organ donation could be significantly reduced. Reproductive cloning is expensive and highly inefficient. More than 90% of cloning attempts fail to produce viable offspring. More than 100 nuclear transfer procedures could be required to produce one viable clone. In addition to low success rates, cloned animals tend to have more compromised immune function and higher rates of infection, tumor growth, and other disorders Many cloned animals have not lived long enough to generate good data about how clones age. Due to the inefficiency of animal cloning (only about 1 or 2 viable offspring for every 100 experiments) and the lack of understanding about reproductive cloning, many scientists and physicians strongly believe that it would be unethical to attempt to clone humans. Peter Terry 10GS Peter Terry 10GS ...read more.

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Here's what a star student thought of this essay

4 star(s)

Response to the question

Overall a well laid out and done piece. Response to the question does not cover asexual reproduction in enough depth, and the process and its examples should be explained in greater scientific detail. The process of embryo transplants is explained ...

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Response to the question

Overall a well laid out and done piece. Response to the question does not cover asexual reproduction in enough depth, and the process and its examples should be explained in greater scientific detail. The process of embryo transplants is explained well and clearly, but again slightly more scientific depth could have been achieved to gain higher marks. A more marked conclusion should be used.

Level of analysis

Asexual reproduction and the process is explained basically. The candidate includes examples but these are quite basic and whilst pictures are used they do not really aid the explanation or clarify how asexual reproduction actually works. However, the process of embryo transplant is explained clearly although the uses of such cloning in animals are not explained explicitly and could be further explained rather than using a table. However, good points are made on the advantages and disadvantages of embryo transplant. Cloning could be explained in a bit more detail but an attempt at a conclusion is made even though it is not an explicit one.

Quality of writing

An extra space is seen in some words which detracts from the meaning of that sentence slightly. Otherwise, grammar, spelling and punctuation are fine. Overall layout is good and flows well.


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Reviewed by skatealexia 01/07/2012

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