Sunday, 25 March 2012

Comparative DNA Analysis in concern to muscular dystrophy identification and accurate diagnosis

The largest human gene, dystrophin, consists of 2,400,000 bases and contains genetic information relating to the musculoskeletal disease, muscular dystrophy[1]. Muscular dystrophy is categorised into specific types of the disease and each of these specific types are found on different combinations on the bases of dystrophin, making diagnosis difficult. If a person were suspected to have muscular dystrophy in the past, scientists would process each of these bases individually, one-by-one to identify the specific type. For instance, Duchenne muscular dystrophy is determined by a combination of 79 different exons but another type of muscular dystrophy may present itself in a totally different combination of exons on the same gene. Exons are the bases that are actually processed to make proteins whereas introns (also known as the ‘junk DNA’) are ignored. Therefore diagnosis was (and still is) difficult as the presence of a mutation on one base could be linked to a number of types of the disease. Diagnosis of the type of muscular dystrophy is important as the types vary in intensity and effect and thus different treatments must be approached. In 2012, Nottingham University’s School of Biology led by Prof. Jane Hewitt in partnership with the Muscular Dystrophy Campaign, undertook a study concerning the accuracy of a machine that could potentially diagnose muscular dystrophy without having to laboriously process each individual base.

The partnership theorised that comparing genes would make the process easier, which proved to be correct. Instead of processing an individual’s genes in an effort to identify mutations, if any, each time a diagnosis was desired, a collection of healthy people’s genes (people who did not have muscular dystrophy) could be compared to a person desiring diagnosis and so the computer could rule out irrelevant gene bases immediately. Then, to determine the type of muscular dystrophy, the machine compares the genes of the person desiring diagnosis to another person who has been diagnosed accurately with a particular type of muscular dystrophy, thus eliminating or verifying diagnosis.

The study used subjects who had been diagnosed inaccurately before to further prove that DNA analysis is the most effective muscular dystrophy diagnostic tool. The study has also endeadvoured for two things to happen as a result of the study. The first aim is for DNA analysis to be more readily available to the public. This is possible now, as each base of the person’s dystrophin does not require individual processing but instead comparison, which is more cost effective. The second aim is for diagnosis to increase in accuracy, which this technology has made possible.[2]

In conclusion, the analysis of genes in concern to identifying diseases is still a difficult process. Comparative analysis is a more accurate and cost-effective technique as it leaves less room for error within identification of the combinations of mutations present on exons and thus the type of disease present.

1.     Leidenroth, A, Sorte, HS, Gilfillan, G, Ehrlich, M, Lyle, R, Hewitt JE 2012, ‘Diagnosis by sequencing: correction of misdiagnosis from FSHD2 to LGMD2a by whole-exome analysis’, European Journal of Human Genetics, doi:10.1038/ejhg.2012.42
2.     Roberts, MBV 1980, ‘Biology: A Functional Approach’ 2nd Ed., Biology Department, Marlborough College, Butler & Tanner Ltd, London.
3.     Urry, Cain, Wasserman, Minorsky, Jackson 2009, ‘Biology: Australia Version’ 8th Ed., Pearson, Australia.
4.     DMD dystrophin [Homo sapiens] 2012, full report, National Center for Biotechnology Information, United States, viewed 17 March 2012,

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[1] See reference item 4
[2] See reference item 1

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