Double Helical Structure

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Structure and function have always had a close relationship in biological, chemical and general terms. Often the functionality is dependent upon the structure, for example the villi on the epithelial cells increase the surface area and hence the rate of absorbance of molecules in to cells and the blood stream. DNAs function is highly specific to its structure as even the smallest change to this could cause a long term effect, or even death. Base sequence mutations, errors in replication and environmental factors are the main cause of changes to DNA.

The structure of DNA was first discovered by James D. Watson and Francis Crick, and in 1962 they won the Nobel prize for discovering this structure, one of the most significant discoveries in the 20th century. This double helical structure is the same for all species, apart from a few strains of virus which have mRNA instead of DNA, and their discovery explained how DNA replicates and how hereditary information is coded.

Deoxyribonucleic acid, or DNA, contains the genetic instructions used in the development and function of all living organisms. The main role of DNA molecules is the storage of information and instructions needed to
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There is a less severe case of this called repeat expansion when shorter nucleotide repeats are repeated a number of times in a row, for example a trinucleotide repeat (TNR) is made up of a 3 base sequence this can cause the resulting protein to function improperly. Usually as the diseased gene is inherited the number of times the sequence is repeated increases. Huntington’s disease(HD) is an example of this, unaffected individuals may have 6-29 CAG triplet repeats, yet in HD patients the disease allele may contain 36 to hundreds of CAG triplets as the TNR repeat number grows with each generation. Over time the mutation in individuals with HD produces huntingtin that causes death of brain cells controlling movement.

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