Foreward

Quantitative Genetics is a traditional subject in many undergraduate animal and plant science programs around the world. Many early quantitative geneticists also crossed over into statistics as they developed methodology to explore variability in domestic plant and animal populations. A lot of the motivation for this study was the interest in unlocking the mysteries of artificial selection as people sought to understand and predict the impact of selection on populations. After World War I, agricultural productivity was becoming increasingly important as fewer people were farming more acreage to produce food for more people. Improving yield and productivity of domestic animals and plants was a key part of this agricultural revolution and genetic selection was an important part of that improvement. As a result, quantitative genetics as an area of study was quite often associated with an agriculture program and many of the historical powerhouses of research and teaching were universities with a significant presence in agriculture.

On the University of Guelph campus, our course in Quantitative Genetics probably originated with the Ontario Agricultural College curriculum which predates the establishment of the university in 1964. For sure, the course has been part of the curriculum here for decades. The course code was originally 40-306 and later became MBG-3060 (MBG being Molecular Biology and Genetics). When I took the course in the fall of 1978 with Dr. Gerry Friars, he had been teaching it for some time, before and after. Others including Drs. Jim Wilton, Ian MacMillan, Brian Kennedy, Larry Schaeffer and John Gibson have also taught the course at some point in time that I know of and each of these folks have contributed to what the course content is today. The oral history in the department reached back to the 1960s and it was on the books back then. When I joined the faculty in 2000, there was an old copy of J.L. Lush’s typed and handwritten notes from the 1930s that came with my office. It had a note inside indicating the volume was removed from the collection of the Ontario Agricultural College library due to its age which strongly suggests that Quantitative Genetics probably started as an OAC course and therefore very likely pre-dates the founding of the university. So with all this tradition on this campus, it seemed to make sense to put together an e-book and virtual course on Quantitative Genetics as a logical step in that legacy and a nod to those before me who taught the course.

I have been teaching MBG-3060 Quantitative Genetics since 2000. I started in the era of overhead projectors with about 100 students and now we’re in the era of AI – artificial intelligence not artificial insemination – with hundreds of students. In 2018 at the 11th World Congress on Genetics Applied to Livestock Production (WCGALP) in Auckland, NZ, I was involved in sessions on genetic education. At the time, MBG-3060 had an in-class and a distance education (DE) section with a total annual enrolment in excess of 450 students. After my presentation I recall some of the questions being around how to teach Quantitative Genetics with that many students, how well did DE work etc. With some of the follow up discussion, I realized that I had experience with one of the largest class sizes of a traditional Quantitative Genetics course and plenty of experience teaching the course remotely. Since then, enrolment has moderated a bit with some changes in pre-requisites to a more manageable 300+ students in an in-class section annually. At the time of writing this in 2026, by my tally I have taught 6,551 students in MBG-3060 in 27 offerings of the course. But what really hit home at WCGALP was a panel discussion where the take home message was the accessibility divide for course materials needed for teaching genetics. Cellphones can provide access to course material almost anywhere in the world but there isn’t much in the way of affordable course material to use in teaching genetics far and wide. And yet, a huge portion of the world’s population is hungry for agricultural productivity and genetics can help with that. Drawing on my experience with the DE section, many years of teaching MBG-3060 and a computer full of course material, it seemed a natural progression to create an accessible e-text and associated quizzes and course materials freely available for teaching Quantitative Genetics anywhere. I started working on gathering materials and researching platforms for distribution when I returned from WCGALP in 2018 but as we know a world-wide pandemic intervened not long after that and the project was sidelined for a while. The material is straightforward but the choice of an online platform was a challenge as well as finding ways to create accessible online equations. Most of those wrinkles have been ironed out and now it is time to put all the pieces together as an e-pub in PressBooks.

This e-book is designed as a mid to upper level undergraduate text covering what I feel is considered classical Quantitative Genetics from Mendelian inheritance to mass selection. I’ve also included some basic QTL detection and Marker Assisted Selection because this is where Quantitative Genetics becomes most relevant again, providing the analysis tools to explore genomes and associations between phenotypes and genotypes. In the appendices you will find sample quizzes for each of the chapter modules. Some of the topics lend themselves to process examples which is best done using video and videos are available from the author. However, in the interest of accessibility and bandwidth, this e-book does not rely on video for illustration- the formulae were challenging enough! Processes are described in words and illustrations.

So what about Quantitative Genetics as a subject? What is really amazing about Quantitative Genetics is that in spite of having foundations that are over 100 years old, the theory is holding up under the renewed scrutiny that came with quantitative trait loci. Although early pioneers in this field were not able to genotype entire populations, they got the theory right. Now that it is feasible and cost effective to genotype a large number of individuals, we have been able to test and use the original theory to analyze and add value to molecular genetic information.

In my own teaching, over the years I noticed that a number of students were successfully using the lecture notes I provided to study the course material on their own. I have also recorded my lectures for over 20 years as a means of providing students with alternatives for how they approach the material. All of the course requirements for MBG-3060 can be met without attending anything except the final exam.

This book approaches the subject from the roots of the course it was developed from – livestock genetics. The examples are derived from livestock but modules have been clustered in a way that hopefully allows for customizing examples to local species and preferences. The notation follows the way I was taught this material and in what seems to be the de facto standard established by the landmark textbook “Introduction to Quantitative Genetics” originally written by Douglas Falconer and first published in the early 1960s. The topic progression is based on over two decades of experience teaching this material in a 12-week semester to a class that grew from about 100 students to over 450 students at peak enrolment.

So with that background as to why we’re here, let’s get started.