A Quantitative Genetics Exercise

 

Paul Willing

Tested Studies in Laboratory Teaching, 2005, Volume 26

Abstract

Our general biology students do two simple Mendelian genetics experiments in their first term, one with Drosophila and one with C-Ferns. Our students also do a natural selection lab using pillbugs (ABLE workshop, 19:307-316), which requires that students understand a little bit about quantitative inheritance. To prepare students for the natural selection experiment, we introduce the lab with a 30-45 minute simulation of inheritance of a multifactorial trait: susceptibility to colon cancer. Each student represents an individual in a population, and is given two alleles of 8 different genes. Each pair of alleles contributes a negative or positive number to their colon cancer susceptibility. Some of the alleles are recessive, some dominant, some partially dominant, some X-linked, and some have an epistatic effect over another gene. Each student adds up his/her susceptibility – a score of zero indicates average genetic susceptibility, a negative number indicates more than average susceptibility, and a positive number means less than average susceptibility. Each pair of students then assumes the role of a married couple; each member of a couple selects one allele of each gene to contribute to their offspring (1 or 2). We record each parents’ and each child’s score for susceptibility to colon cancer in an EXCEL spreadsheet and project this on the screen for class discussion. This exercise also helps students learn a little about population genetics, partial dominance, epistasis, X-linked inheritance, etc.

Keywords:  quantitative genetics

Bowling Green State University, Ohio (2004)