Q1)Find out the relative timing of the events and place them in the correct orde
ID: 23760 • Letter: Q
Question
Q1)Find out the relative timing of the events and place them in the correct order from the least recent to the most recent. If research leading to this invention, event, or finding spanned many years use the date of the project's completion in the time series.Discovery of the PCR Technique
Invention of the electron microscope
Discovery of the role of cyclic AMP in cell signalling
Discovery of the chemical structure of DNA
Discovery of the cell as a unit
Understanding of the mechanism the light-independent reaction of photosynthesis
Cell culture technique first developed
Birth of Dolly, the cloned sheep
Discovery that DNA is the genetic material
Invention of Southern Blotting
Explanation / Answer
PCR Technique : Scarcely any invention has altered biological science so radically in such a short period as the polymerase chain reaction, or PCR. With this technique, minute amounts of DNA can be replicated very rapidly and thereby amplified to such an extent that the DNA becomes easy to detect, study and use for any given purpose. The potential of this technique in medicine has long been known, and ever more applications are being developed. Wherever genes provide clues to the cause or natural history of a disease, PCR is the method of choice. Terms: DNA deoxyribonucleic acid; the chemical substance of our genes RNA ribonucleic acid; the chemical substance that makes up the working copies of genes (mRNA), among other things Nucleic acids a chemical term that covers both DNA and RNA; nucleic acids are molecules consisting of long chains of nucleotides linked together Nucleotides the building blocks of DNA; they comprise the four bases adenine, thymine, cytosine and guanine (A, T, C, G; in RNA thymine is replaced by uracil [U]), a sugar and at least one phosphate group; without the phosphate group these building blocks are referred to as nucleosides Sequence the order of the nucleotides in DNA (DNA sequence) or RNA (RNA sequence) Primer a short DNA fragment with a defined sequence that serves as an extension point for polymerases Polymerases enzymes that link individual nucleotides together to form long DNA or RNA chains Hybridisation (annealing) the joining of two complementary DNA (or RNA) strands to form a double strand Complementary DNA The building blocks of DNA and RNA form specific pairings. Two strands whose building blocks form a sequence of perfect pairings are able to form a stable double strand and are referred to as complementary strands. Rapid DNA cloning: In the PCR procedure trace amounts of DNA can be quickly and repeatedly copied to produce a quantity sufficient to investigate using conventional laboratory methods. In this way, for example, it is possible to sequence the DNA, i.e. determine the order of its building blocks. Theoretically, a single DNA molecule is sufficient. PCR is therefore one of the most sensitive biological techniques ever devised. Given these capabilities,Mullis’s method ultimately ushered in the age of genomics. From the Human Genome Project to the search for targets to the development of gene tests, there are few areas ofgenetic research today that do not depend on PCR. Only with the advent of increasingly sensitive DNA chips in recent years has PCR faced any notable competition (see chapter on DNA chips). But even then it is often necessary to first copy, or amplify, the DNA of interest. For this reason PCR and DNA chips often go hand in hand. Dolly the sheep: Scientists in Scotland have announced the birth of the world's first successfully cloned mammal, Dolly the sheep. Dolly, who was created at the Roslin Institute in Edinburgh, was actually born on 5 July 1996 although her arrival has only just been revealed. Dolly is the first mammal to have been successfully cloned from an adult cell. Previous clonings have been from embryo cells. The sheep's birth has been heralded as one of the most significant scientific breakthroughs of the decade although it is likely to spark ethical controversy. Scientists in Scotland cloned a ewe by inserting DNA from a single sheep cell into an egg and implanted it in a surrogate mother.They now have a healthy seven-month-old sheep - Dolly - who is an exact genetic duplicate of the animal from which the single cell was taken.DNA tests have revealed that Dolly is identical to the ewe who donated the udder cell and is unrelated to the surrogate mother. DNA genetic material: We need to discuss this in an historical context. During the 19th century most scientists thought that a bit of the essence of each and every body part was put into the sperm and egg and that at conception a blending essences occurred. This theory was called Blending Inheritance. It was based on a non-rigorous observation of nature. Complex characteristics were examined and careful counts of the number and type of progeny were not performed.It is not correct. A simple example of one of Mendel's experiments. Here 'A' causes the pea to be dark in color and 'B' causes it to be smooth. 'a' causes it to be light in color and 'b' causes it to be wrinkled. 'A' and 'B' are dominant to 'a' and 'b' respectively. In the F1 generation all of the progeny are dark and smooth.
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