Mapping And Analysis of Quantitative Trait Loci (QTL) for Binary Distributed Data

• Main Authors: Chiang, Chih-ming, 江志民
• Other Authors: Ching Liu
• Format: Others
• Language: zh-TW
• Published: 1998
• Online Access: http://ndltd.ncl.edu.tw/handle/51486537381198249938

碩士 === 國立臺灣大學 === 農藝學系研究所 === 86 === Most quantitative traits are assumed to be continuously and normally distributed. Due to the nature of response, limitation of measurement or some other theoretical or practical considerations, only the discrete binary data are available. Published statistical methods for mapping and analyzing quantitative trait loci(QTL) all center on the normal assumption and thus can not be directly applied for binary distributed data. This study proposes a logistic mixture regression model for binary distributed data based on simple interval mapping(SIM) and composite interval mapping(CIM) respectively. Iteratively reweighted least squares(IRLS) derived by expectation- maximization(EM) algorithm is used to obtain the maximum likelihood solutions of the effects and positions of QTLs. The methods presented in this paper are conceptually simple, easy to implement and fast in convergency. Results from simulated F2 intercross data indicate the proposed methods can effectively detect the putative QTLs. Method based on SIM has higher power than method based on CIM for the case of single QTL on each chromosome. Method based on SIM becomes less effective than method based on CIM when there are two or more QTLs on each chromosome, especially when QTLs are close together. In other words, method based on CIM has higher resolution than method based on SIM when there are two or more QTLs on each chromosome. However, interpretation of genetic parameters is more difficult for CIM model than for SIM model. Since number of QTLs on each chromosome is not known in practice, both CIM and SIM models should be tested and compared for any particular set of data. Two linked QTLs are not likely to be distinguished by both the methods studied if the distance between QTLs is less than about 20cM.