Assessment of risk has been a key element in efforts to identify factors associated with disease, to assess potential targets of therapy and enhance disease prevention and treatment. Considerable work has been done to develop methods to identify markers, construct risk prediction models and evaluate such models. This dissertation aims to develop robust approaches for these tasks. In Chapter 1, we present a robust, flexible yet powerful approach to identify genetic variants that are associated with disease risk in genome-wide association studies when some subjects are related. In Chapter 2, we focus on identifying important genes predictive of survival outcome when the number of covariates greatly exceeds the number of observations via a nonparametric transformation model. We propose a rank-based estimator that poses minimal assumptions and develop an efficient

This study was performed for the identification of specific DNA marker using RAPD-PCR (Random Amplified Polymorphic DNA) method for serotype Salmonella Typhimurium which is one of the most prevalent serotype causing food poisining all over the world. The Primer 3 (RAPD 9.1), 5&rsquo / -CGT GCA CGC-3&lsquo / , was used in RAPD-PCR with 35 different Salmonella isolates. 12 of them were serotype Salmonella Typhimurium and 23 of them were belonging to other six different serotypes. Accordingly, two different 300 bp and 700 bp sized amplification products were obtained from the 12 different Salmonella Typhimurium isolates. On the other hand, other 23 Salmonella isolates of six different serotypes gave only 300 bp amplification band while 700 bp amplification band was not observed with Primer 3 (RAPD 9.1). After the discovery of 700 bp fragmentwhich was specific for S. Typhimurium, it was decided to sequence. The 700 bp band was ligated onto the vector pUC 19 to sequence. The cloninig operation gave positive results by the formation of blue and white colonies, but plasmid isolation process from white colonies containing the ligated vector was not achieved. Therefore, sequencing of the 700 bp fragment together with plasmid DNA could not be completed. However it wil be sent to USA for sequencing. According to these results, it was discovered that 700 bp amplification product was found as a specific polymorphic region for Salmonella Typhimurium after RAPD application on genomic DNA and this band can be used as a specific marker for detection and identification of Salmonella Typhimurium.