Quiz 13: Dna Structure and Function


Escherichia coli or E. coli is a small bacterium, which cannot be visible to the naked eye. The bacteria are normally harmless and live in our gut and help in digestion process and protect us from other harmful bacteria. E.coli has been very useful in industries, in producing some important products and also it helped scientists in their experiments. The bacterium is one of the first organisms whose whole genome is sequenced. But suddenly one day a pathogenic strain of E.coli evolved from it, which has created havoc by producing a dangerous toxin especially in young children who eat undercooked or raw beef. Scientists started doing research on the evolved bacterium and found that the pathogenic strain also consists of the genes that are almost similar to the harmless strain of E.coli. In addition, they also found that newly evolved bacterium contains some extra genes, which are responsible for the pathogenesity. The presence of extra genes might be the reason for viral infection of the strain. When a virus infects the bacteria, genetic material of the bacteria changes by adding extra harmful genes to it and making it a pathogenic. Another reason might be that E.coli has the capability to swap genes that have the capability to swap genes with other harmful bacteria; hence the genes lead to the pathogenicity of E.col i.

Uracil is not a nucleotide base in DNA. Uracil is a nucleotide base of RNA, which is proven as the first genetic material. DNA is evolved from RNA and uracil is replaced with THYMINE due to some scientific examples, which may prove this Thymine structure is also similar to uracil except for the methyl group i.e. why it is called as 5-Methyl Uracil. Uracil has the tendency to bind to any groups, but by evolving it to thymine it can bind to adenine avoiding other groups in the double helix. Cytosine by deamination becomes uracil, so in order to distinguish this uracil from original uracil, it is better way of replacing it with Thymine, but this process is all done manually by any individual it is all due to evolution. No one knows why and when evolution occurs and the changes it can cause.

A-T, G-C is the base-pairing rules for DNA. According to Watson and Crick model, the DNA structure is double helix, and the base pairs which are formed between specific nitrogenous bases (A-T and G-C) are the building blocks of the structure of DNA and stabilize it in folded form. Hydrogen bonds pair the bases, A and T are bonded by 2 H-bonds and G and C are bonded by 3 H- bonds. This bonding provides a backup copy of the genetic information encoded in the DNA.

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