Two Celled Embryo example essay topic

: Human cloning -- a controversy When the personalities of two individuals seem impeccably compatible, people often say in jest that they are "made from the same mold". With the recent scientific breakthroughs and the technology that make them possible, this abstract clich'e is becoming more plausible. The fast growing pace of scientific discoveries, such as human cloning, forces our society to finally open its eyes and accept the new and astonishing possibilities. Human cloning not only advanced rapidly throughout the past couple of years but also has raised many controversies due to its benefits and also disadvantages. Cloning is not an innovative idea; in fact, it is almost if not even older than agriculture- one of man's earliest and most successful means of survival. Cloning has been going on in the natural world for thousands of years.

For example, if or whenever a gardener takes a cutting from one plant and places it in a medium (such as water), it will grow again - this is a basic example of cloning. A clone is simply one organism made from another, resulting to two organisms with the same set of genes. (Block, par. 17) In that sense, identical twins are clones, because they have the same DNA. When earthworms are cut in half, they regenerate the missing parts of their bodies, leading to two worms with the same set of genes. The original purpose of cloning was simply to multiply an organism without waiting for nature to act on it first.

Farmers were in favor of this because it helped them improve the medium or elements of the planets which make it stronger, thicker, more resistant to disease, and therefore better survivors in nature. What we now call genes were first described by an Austrian monk named Gregor Mendel. Genes are some of the smallest parts of each living organism, animal or plant. They are groups of chemicals contained in each of the billions of cells that make up our bodies. They break off into codes that determine our gender, height, eye color, etc. In short, they determine who we are.

Mendel was interested in the differentiation between plants and flowers and how they came to be. He wanted to learn ways to change the color, size, rate of growth and even traits. Starting in 1865, Mendel began a series of experiments in which he crossbred different flowers by taking the pollen from one type and transferring it to another. This also happens in nature when, for example, a bee carries pollen from one type of flower to another. Mendel, in this case meticulously took data of every type of change that occurred when the crossbred plants reproduced (also called hybridizing of plants).

He soon established the Law of Segregation, which basically states that during the formation of gametes, they each receive one member of a pair of homologous chromosomes. Mendel decided that the seeds of the new crossbred must contain a pair of each allele that determined a planet's characteristics. He considered one of these alleles to be dominant, or stronger, and the other recessive, or weaker. The dominant will most likely determine the characteristics of a plant while the recessive allele would come back in later generations of the new plant.

Mendel's observations and theories played a huge role in later discoveries dealing with genes as well as modern scientific breakthroughs. Another important figure in the history of cloning is Hans Dreisch. In the late 1800's, he performed series of experiments with sea urchins to discovery that, contrary to beliefs, genetic material is not lost during cell division. Dreisch believed sea urchins to be suitable for testing because they have relatively large embryo cells, and grow independently of their mothers. Dreisch took a two-celled embryo, placed it in sea water solution and watched it divide into two separate cells. Each then grew independently and indeed formed two separate whole sea urchins.

From there, no major discoveries in cloning were made until November of 1951 when a team of scientist cloned a frog embryo in Philadelphia. Unlike experiments before, this team did not just break off a cell from an embryo; they instead took the nucleus out of a frog embryo cell and used it to replace the nucleus of an unfertilized frog egg cell. Once the egg cell detected that it had a full set of chromosomes, it began to divide and grow. (Block, par. 13) This was the first time that this process, called nuclear transplant, was ever used, and it continues to be used today, although the method has changed slightly.

Finally, a breakthrough came in 1986. A mammal was cloned by two independent teams using the same method. In England, a team led by Steen Willadsen cloned a sheep's embryo while Neal First, who led the team in America cloned a cow's embryo. This was a huge step forward in scientific accomplishments because many advances of different types were made during these experiments, including usage and invention of innovative technology, and discovery that tissue could be kept alive in lab conditions. In the most recent case regarding cloning, a lamb was born under the meticulous care and studies of Ian Wilmut at the Roslin Institute in Scotland on July 5th, 1996, Wilmut, who names his animals very creatively, named her Dolly after Dolly Parton. Experiments involving human beings were never even considered until recent technology and advanced scientific methods that allowed the creation of Dolly.

The scientific community was shocked by her birth and continued to investigate further on the topic of human clones. The new technique used in cloning Dolly the sheep was called nuclear transfer. Her DNA came from a single cell taken from her mother's egg, which is fused with the mammary cell. After the fused cell develops into am embryo, it is then implanted in a substitute sheep. This embryo then grows into a lamb that obtains the same genes as its donor sheep. The process seems clear and concise but its procedure took a long time to perfect.

Dolly was finally created as a healthy lamb after more than 277 attempts. (Block, par. 35) That is a part of the reason cloning has become controversial -- scientists fear that applying this technique to humans may lead to malformations or diseases in the human clone. Moreover, human cloning is even more complicated, with greater risks, permanent damage, and potentials for error.