Posts
The jury is still out. There is evidence that the length of the chromosome ends called telomeres are associated with ageing. Dolly has shorter telomeres than expected and so the suggestion is that the fact that she was cloned from a six year old ewe may have some effect. Significantly Dolly has given birth to three sets of lambs by ordinary mating, and they show normal telomere length. Other experiments in the USA claim that
cloning can produce longer telomeres, implying apparently younger animals.
This is an indication that, despite the empirical results, the basic science of nuclear transfer cloning is still comparatively little understood.
Custom Search
The Humane Society of the United States condemns the commercial cloning of companion animals. Given the current pet overpopulation problem, which costs millions of animals their lives and millions in public tax dollars each year, the cloning of pets has no social value and in fact may lead to increased animal suffering.
Cloning is an imperfect science and potentially dangerous for the animals involved, including the clone. Many animals cloned thus far have had a wide range of medical complications. Whether a cloned companion animal can lead a healthy and full life remains unknown. In addition, surrogate mothers who bear the cloned embryos until delivery may have to endure
surgical procedures due to complications from pregnancy.
For those looking to replace a lost pet, cloning will not create an animal identical to the one who is gone; cloning cannot replicate an animal's uniqueness. Cloning can only replicate the pet's genetics, which influence but do not determine his physical attributes or personality. In fact, a pet's personality, the specific trait that most owners would like to preserve and the attribute that most endears a companion animal to his family, is the trait least likely to be replicated by cloning. In addition, there is no guarantee the cloned companion animal will even physically resemble the original pet.
Components of DNA
DNA is a polymer. The monomer units of DNA are nucleotides, and the polymer is known as a "polynucleotide." Each nucleotide consists of a 5-carbon sugar (deoxyribose), a nitrogen containing base attached to the sugar, and a phosphate group. There are four different types of nucleotides found in DNA, differing only in the nitrogenous base. The four nucleotides are given one letter abbreviations as shorthand for the four bases.
- A is for adenine
- G is for guanine
- C is for cytosine
- T is for thymine
What is DNA?
The work of many scientists paved the way for the exploration of DNA. Way back in 1868, almost a century before the Nobel Prize was awarded to Watson, Crick and Wilkins, a young Swiss physician named Friedrich Miescher, isolated something no one had ever seen before from the nuclei of cells. He called the compound "nuclein." This is today called nucleic acid, the "NA" in DNA (deoxyribo-nucleic-acid) and RNA (ribo-nucleic-acid).
Two years earlier, the Czech monk Gregor Mendel, had finished a series of experiments with peas. His observations turned out to be closely connected to the finding of nuclein. Mendel was able to show that certain traits in the peas, such as their shape or color, were inherited in different packages. These packages are what we now call genes.
For a long time the connection between nucleic acid and genes was not known. But in 1944 the American scientist Oswald Avery managed to transfer the ability to cause disease from one strain of bacteria to another. But not only that: the previously harmless bacteria could also pass the trait along to the next generation. What Avery had moved was nucleic acid. This proved that genes were made up of nucleic acid.
