Why is sexual reproduction so common in nature?
Why is sexual reproduction so common in nature? One of the greatest challenges for evolutionary biology is explaining the widespread occurrence of sexual reproduction, and the associated process of genetic recombination. Sexual reproduction involves one individual combining half its DNA with half of DNA of another individual, so that the offspring is only half genetic copy of each parent. However, in asexual reproduction, the offspring are genetic copies of the parent. Thus, sexual reproduction poses an evolutionary problem because it seems to be half as efficient a method of reproducing as asexual reproduction. Asexual females can potentially produce twice as many daughters as sexual females, so that the ratio of asexual to sexual females should initially double each generation, resulting in the 'two-fold cost of sex'.? In addition to this 50% cost and the dilution of the individual's genome, sexual reproduction also presents other disadvantages in comparison to asexual reproduction. First and foremost there is the cost of recombination - favourable gene combinations that have increased in frequency under the action of natural selection are broken up. Secondly, the process of sexual reproduction requires a significant cellular-mechanical cost as sex requires meiosis, syngamy and karyogamy. A great amount of time is taken up by these three processes alone, and far
Cloning pros and cons
Cloning A group of genetically identical offspring produced by asexual reproduction is called a clone. The nucleus of every cell of an individual contains the genetic information needed to develop the entire organism. It is therefore possible under suitable conditions to produce a whole organism from a single cell. If a cell divides mitotically it will produce a clone. If each cell of the clone is separated and allowed to develop into the complete organism, a group of genetically identical offspring is formed. This is known as cloning. (2). Two very different procedures have been referred to as "cloning": * Embryo cloning has been successfully carried out for years on many species of animals. Some limited experimentation has been done on human embryos. * Adult DNA cloning has been used to clone a sheep, but was not tried on humans until 1998-DEC (3) Humans often think of themselves as being superior to other animals (not to mention plants, fungi, bacteria and so on) and therefore having the "right" to exploit other organisms for their own benefit. (1) The cloning of the sheep, Dolly, in 1997 was an inevitable consequence of the progress being made in genetics and biotechnology. It raises the possibility of breeding many identical copies of animals including transgenic animals, showing desirable features. One of the ethical concerns is that the techniques could be
Embryo Screening. The embryo screening, also referred as PGD (preimplantation genetic diagnosis), is a procedure tested on an embryo to identify any unwanted diseases that is found in the genes of the embryo.
Embryo Screening Settling down and starting a family is what many couples have in mind. It's a life changing decision the many indivisual choose to endure, however, obstacles and complications have delayed couples from fulfilling their goal. Leaving the chances of pregnancy aside, couples try to prevent many issues that occur with their newborns - infectious and complicated diseases, deformities and abnormalities. In many cultures and races, it is customary, or even the norm, to marry close relatives. This scientifically has been proven to increase the chances of having your offspring inherit the diseases that have been in the past generations, such as diabetes, cancer, anemia and leukemia. [8] One type of solution that has been discovered is embryo screening and human genetic engineering. The embryo screening, also referred as PGD (preimplantation genetic diagnosis), is a procedure tested on an embryo to identify any unwanted diseases that is found in the genes of the embryo. This then enables the couples to be aware of the problems that they might be facing if they do get pregnant, and leaving their embryo untouched. After enlightening couples about the genetic diseases found in the genes, they have to whether to go through the PGD and modify the genes to contract the ones that contain the genetic information about the disease, abnormality, or deformity. "PGD involves
Genetically modified crops - Do we know all the answers?
Genetically Modified Crops. Do we know all the answers? Genetic Modification is the method of obtaining individual genes, which are then copied and repositioned into another living organism to modify its genetic code and incorporating or removing particular characteristics into or from an organism.1 There are many viewpoints on the issue genetic modification, some scientifically based on environmental factors and potential economic growth, others concerning ethical, moral and social perspectives. Ever since the breakthrough of genetic modification, deliberation has surrounded all issues involving this controversial topic. Many organizations have published books, videos, and leaflets arguing their side of this debate. Advances in GM biotechnology, such as the incorporation of the gene which stops the Arctic Flounder from freezing, has been placed into the genetic sequence of strawberries to stop them shrivelling in the cold British weather2, these 'modifications' have led to many intrinsic and extrinsic moral issues arising from this "new" technology. Dr Robert Farley of the Monsanto Institute, USA3 believes that genetic modification of crops for human consumption is a much more efficient and effective way of creating more resilient wheat crops than traditional cross-pollination. This is because genetic modification is more specific in changing a particular gene,
