Testing for Heterosis in Gene Expression

• Activity Number: 39
• Type: Contributed
• Date/Time: Sunday, July 29, 2012 : 2:00 PM to 3:50 PM
• Sponsor: IMS
• Author(s): Heng Wang*+ and Daniel Nettleton
• Companies: Iowa State University and Iowa State University
• Keywords: heterosis ; gene expression ; likelihood ratio test ; union-of-cones

Abstract

Heterosis, also known as hybrid vigor, occurs when the mean trait value of offspring is more extreme than that of either parent. For maize, this phenomenon was first documented in the late 1800s and is the basis of the seed corn industry today. In an effort to understand the molecular genetic mechanisms responsible for heterosis, researchers have begun to measure the expression levels of thousands of genes in parental maize lines and their offspring. We will discuss statistical tests that can be used to identify genes that exhibit heterosis in their expression. The testing problem is nonstandard because the null hypothesis of no heterosis is a union of two essentially disjoint closed convex cones that is neither a cone nor convex. We will present the likelihood ratio test for this problem and discuss the existence and characteristics of uniformly more powerful tests, which can be constructed using strategies employed by Berger (1989) and Zelterman (1990) for the problem of identifying qualitative interactions.