Sciences dissertation examples

Recent advances in dna sequencing technologies

Recent advances in DNA sequencing technologies have led to efficient methods for determining the sequence of DNA. DNA sequencing was born in 1977 when Sanger et al proposed the chain termination method and Maxam and Gilbert proposed their own method in the same year. Sanger's method was proven to be the most favourable out of the two. Since the birth of DNA sequencing, efficient DNA sequencing technologies was being produced, as Sanger's method was laborious, time consuming and expensive; Hood et al proposed automated sequencers involving dye-labelled terminators. Due to the lack of available computational power prior to 1995, sequencing an entire bacterial genome was considered out of reach. This became a reality when Venter and Smith proposed shotgun sequencing in 1995. Pyrosequencing was introduced by Ronagi in 1996 and this method produce the sequence in real-time and is applied by 454 Life Sciences. An indirect method of sequencing DNA was proposed by Drmanac in 1987 called sequencing by hybridisation and this method lead to the DNA array used by Affymetrix. Nanopore sequencing is a single-molecule sequencing technique and involves single-stranded DNA passing through lipid bilayer via an ion channel, and the ion conductance is measured. Synthetic Nanopores are being produced in order to substitute the lipid bilayer. Illumina sequencing is one of the latest sequencing technologies to be developed involving DNA clustering on flow cells and four dye-labelled terminators performing reverse termination. DNA sequencing has not only been applied to sequence DNA but applied to the real world. DNA sequencing has been involved in the Human genome project and DNA fingerprinting.

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Tobacco parasitic nematode

Tobacco (Nicotina tabacum L.) is one of the most important non- food crop and widely grown commercially (Akerhust, 1981). This plant had a high economic value and widely demanded throughout the world for the usage of the nicotine, cigarettes, cigars and other tobacco product (Akerhust, 1981).

Nowadays, in Malaysia, Tobacco industry is very crucial in uplifting the socio-economic status of farmer in Kelantan, Terengganu, Kedah and Perlis. There were 20,524 farm families, 355 tobacco curers, 1300 grower and 25384 station workers. This industry generates about 150 million in income per year. 38% of the income goes to the farmers and 18% to the curers (http://www.malaysiayellowpages.net/mpi/details/TOBACCO.htm). This plant can give a stable income and therefore increased the income of farmer (Wells, 1987). Tobacco was cultivated as a rotation with the paddy for a side income (Anon, 1981). Tobacco plant can be infected by bacteria, fungus, virus, and parasitic nematode. Disease infection lower the tobacco yield and also quality. This research focused on effect of plant parasitic nematode on tobacco.

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