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This e-book presents a series of topics in classical Quantitative Genetics in a progression from the re-discovery of Mendel’s discovery of inheritance of alleles through exploring genetic variation and culminating in the basics of detecting regions of the genome that influence phenotypes. The material begins at a point that assumes students have been introduced to the rudiments of genetics in biology so it is assumed that the segregation of chromosomes during meiosis and the inheritance of DNA through haploid gametes is understood.

This e-book assumes a diploid genome and haploid gametes as is typical of virtually all domestic livestock except salmonids farmed in aquaculture, and even for those fishes the theory will generally work with little or no modification for ploidy differences. Sex determination is generally assumed to be the mammalian X-Y system but adapting the theory to the avian Z-w system is presented and briefly discussed.

Each chapter, except this one, has an associated set of practice problems. When MBG-3060 is taught with this material, each chapter is generally treated as a weekly module with associated quiz components – a practice quiz and a graded quiz. Each weekly practice quiz provides students the opportunity to become familiar with the previous week’s theory and associated formulae by providing a set of randomized questions that can be completed and submitted for immediate feedback and guidance in the case of incorrect answers. The practice quiz can be completed multiple times. Following mastery of the material via the practice quiz, students would then complete the graded quiz as a formative assessment of their understanding of the theory. In addition to formula-based questions, the graded quizzes include an add-on component usually consisting of five questions designed to encourage students to think about real-world applications of the theory they have just mastered.

For an added bit of fun, as the course material progresses, the major socio-political and pop culture happenings in the world and on our campus when the particular bit of theory was developed are also presented. With course material like this that has roots well over a century ago, a lot has happened along the way and added contextual references help illustrate the world the researchers lived in while doing their work and what the Ontario Agricultural College looked like at the time. So many things are taken for granted now – computers, the internet etc etc. Those didn’t exist when most of the material in this e-book was being researched and discovered so having world and local historical reference points helps remind students of the different conditions under which scientists were working in days gone by. Since most of those historical references are slanted to the Guelph course offering, they are not included in this e-book.

The e-book and the course it is based on are organized around a circle. The starting point is considering a single locus and examining allele frequencies and the impact of selection, migration and (briefly) mutation on those allele frequencies. Then we add in additional loci and look at how a few loci work together when we know all of the loci that are involved. Following that, we expand the situation to many loci working together to create a phenotype when we can no longer pick out individual loci and instead work with all loci in aggregate ways. And then we come back around to a single locus where we can explore the genome and identify an individual locus associated with a phenotype and work with both that one locus and the rest of the myriad of loci influencing the same phenotype.

In genetics, the most over-worked word is “gene”. To add to student confusion, the term “gene” is used to mean different things. Some will talk about a gene when they are referring to a locus on a chromosome while others will talk about a gene when they are referring to an allele. In this e-book, we will rarely use the word gene and instead, more precisely refer to either a locus or an allele to avoid that confusion.

Key terms are presented with a glossary entry as you may have already noticed. Terms with a glossary entry are often part of the lexicon of the discipline. Students who wish to pursue further studies in genetics may want to become proficient with the lexicon of the discipline as well as the theory and concepts.