DNA Replication

The goal of DNA replication is the amplification of existing DNA. During cell division, the DNA of the cell is exactly duplicated and then distributed to both daughter cells. The doubling of DNA takes place according to the so-called semi-conservative principle, which means that after the initial unravelling of the DNA, the original DNA strand is separated by an enzyme (helicase) and each of these two “original strands” serves as a template for a new DNA strand.

The DNA polymerase is the enzyme responsible for the synthesis of the new strand. Since the opposite bases of a DNA strand are complementary to each other, the DNA polymerase can use the present “original strand” to arrange the free bases in the cell in the correct order and thus form a new DNA double strand. After this exact duplication of the DNA, the two daughter strands, which now contain the same genetic information, are divided between the two cells that were formed during cell division. Thus, two identical daughter cells have emerged.

History of DNA

For a long time, it was unclear which structures in the body are responsible for passing on our genetic material.Thanks to the Swiss Friedrich Miescher, the focus of research in 1869 was on the content of the cell nucleus. In 1919 the Lithuanian Phoebus Levene discovered the bases, the sugar and the phosphate residue as building material for our genes. In 1943, the Canadian Oswald Avery was able to prove with bacterial experiments that DNA and not proteins are actually responsible for the transfer of genes.

In 1953, the American James Watson and the British Francis Crick put an end to the research marathon that had spread over many nations. They were the first to use Rosalind Franklin’s (British) DNA x-rays, a model of the DNA double helix including purine and pyrimidine bases, sugar and phosphate residues. However, Rosalind Franklin’s X-rays were not released for research by herself, but by her colleague Maurice Wilkins.

Wilkins was awarded the Nobel Prize for Medicine in 1962, together with Watson and Crick. Franklin had already died by this time and could therefore no longer be nominated. This topic could also be of interest to you: Chromatin Criminalistics: If suspicious material is found, such as at a crime scene or on a victim, DNA can be extracted from it.

Apart from genes, DNA contains more sections consisting of frequent repetitions of bases and does not code for a gene. These intermediate sequences serve as a genetic fingerprint because they are highly variable. The genes, however, are almost identical in all people.

If the DNA obtained is now cut up with the help of enzymes, many small DNA sections, also called microsatellites, are formed. If one compares the characteristic pattern of the microsatellites (DNA fragments) of a suspect (e.g. from a saliva sample) with that of the existing material, it is highly probable that the perpetrator will be identified if they match. The principle is similar to that of fingerprints.

Paternity test: Again, the length of the child’s microsatellites is compared with that of the possible father. If they match, paternity is very likely. Human Genome Project (HGP): The Human Genome Project was established in 1990.

James Watson initially led the project with the goal of deciphering the entire code of DNA. Since April 2003, the human genome has been considered completely decoded. 3.2 billion base pairs could be assigned to about 21,000 genes. The sum of all genes, the genome, is in turn responsible for several hundred thousand proteins.

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