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As teachers of genetics and the authors of An Introduction to Genetic Analysis, we are aware of the quiet revolution in the way that genetics is taught to beginning students. Many instructors are finding that a strictly chronological, or historical, approach no longer fits their method of teaching genetics, nor does it meet their students’ needs. More and more, molecular genetics is being introduced earlier in the course and integrated with phenotypic and genotypic analysis.
Modern Genetic Analysis was written for instructors and students who need a textbook that supports the “DNA first” approach. This departure from the traditional historical unfolding of genetics has had some significant side effects—chief among them, a more streamlined presentation in which genetic principles stand in bolder relief.
Regardless of whether the presentation is traditional or modern, it is essential that students learn to think like geneticists. Thus, as in An Introduction to Genetic Analysis, the focus is on teaching students to analyze data and draw conclusions.Figure 1-10
After an introductory chapter on the relations between genes and phenotypes, there is a chapter on the structure of genes and genomes. This immediately establishes a framework of the molecular nature of the hereditary material on which its various properties can be hung. Chapters 3 through 5 deal with gene function and gene inheritance, which are related back to the structural nature of the genome. Chapter 4, “The Inheritance of Genes,” presents the inheritance patterns of single genes. Increasing complexity stepwise, Chapter 5, “Recombination of Genes,” covers the principles at work when two genes or more are analyzed. We add further to the complexity of genetics in Chapter 6, “Gene Interaction,” in which inheritance patterns are related to functional gene interactions at the molecular level.
Thus, in the first six chapters, the core of our modern view of gene structure and function is presented. However, instead of segregating Mendel’s work in its own chapter, we have extracted the principles deduced by Mendel and integrated them where they belong pedagogically, alongside the cellular and molecular structures that drive them. Our belief is that this new organization of material will help those students who have trouble retrospectively fitting molecular biology onto a framework of Mendelian genetics. Moreover, because molecular biology is introduced first, we provide an opportunity for a vertical integration of concepts at the organismal, cellular, chromosomal, protein, and DNA levels. Finally, we hope that this new approach will enable students to understand how genetics is done in the “real world,” where classical and molecular approaches are not segregated but complement each other.
In keeping with the book’s title, we have strived for currency throughout the text. We have included the latest approaches in genomics, including a section on functional genomics embracing DNA chip technology and the yeast two-hybrid system. As another example, programmed cell death is considered in the contexts of both normal biology and the genetics of cancer.Figure 3-28 Figure 3-25 Figure 15-4
A primary goal in writing Modern Genetic Analysis was that the understanding and application of core genetic principles take priority over historical details. We hope that students will more readily recognize and grasp fundamental principles and themes if their presentation is not encumbered by excessive detail. Thus the focus is on overarching principles of genetics rather than the historical experiments that generated them. The principles are used to explain to students how genetics is done today. For instance, in Chapter 3, we introduce the common themes of complementarity of nucleic acid sequences and specificity of protein– nucleic acid interactions. Students then see these themes again in subsequent chapters, applied in the analyses of DNA replication, protein synthesis, and regulation of gene expression.
In all chapters, we stress the vertical relation between DNA, protein products, and phenotype. The chapters on recombinant DNA technology focus on how recombinant DNA technology is used to isolate and characterize genes, rather than on the techniques themselves. Here the students will see how recombinant DNA techniques were used to clone the human genes for albinism and alkaptonuria. In Chapter 11, “Applications of Recombinant DNA Technology,” a section deals with transgenic crops currently in use in agriculture. The chapters on developmental genetics emphasize the importance of signal transduction cascades in all aspects of a cell’s or an organism’s development and the important and varied switch mechanisms that underlie all developmental decisions.
Although we do not want the details of historical experiments to distract from the core principles, it is enriching in a well-rounded study of genetics for the students to be exposed to some of the landmark experiments in genetics. Students benefit from learning how these key experiments were conceived and carried out. These important investigations are set apart from the text in sections called “Genetics in Process.”
Here,
students will read about the way that Archibald Garrod inferred the nature of inborn
errors of metabolism, about the research that led Charles Yanofsky to deduce that
gene and protein structure are colinear, about Watson and Crick’s model
for the structure of DNA, including Watson’s own description of the first
assembly of the metal model, and about Luria and Delbruck’s method of
deducing the random nature of mutations.Figure
4-20
We focus on the questions that underlie much of modern genetics, such as, “How many genes affect this phenotypic difference? Are the genes linked? Are the mutations allelic? What is the cellular function of the gene?” In short, the focus is on the modes of inference used in genetics today.
PROBLEMS at the end of each chapter have been created for students to apply and exercise their analytical skills. Problems are arranged to start from the simple and proceed to the more complex. All problems have been classroom tested. Of particular interest is a new type of problem called Pattern Recognition.
These problems are symbolic representations of the results of simple cross
systems, shown graphically with a minimum number of words. They have been designed
to aid students in recognizing hereditary patterns in data, a key skill in genetic
analysis. Most chapters also include a problem containing an exercise titled Unpacking the Problem.
. Such exercises reveal the underlying levels of knowledge that must be
applied for a problem to be solved constructively. The unpacking exercise accesses
this underlying knowledge and even addresses fundamental misunderstandings that
sometimes prevent students from solving problems successfully.
Each chapter also includes several SOLVED PROBLEMS
that walk students through the way in which geneticists apply
principles to experimental data. The Solved Problems prepare students for solving
problems on their own.
KEY CONCEPTS at the beginning of each chapter give an overview of the main principles to be covered in the chapter, stated in simple prose without genetic pinology. They provide a strong pedagogic direction for the reader.
Highlighted MESSAGES
appear throughout each
chapter to serve as convenient milestones at which the reader can pause and
contemplate the material just presented.
Each chapter SUMMARY
provides a short
distillation of the chapter material and an immediate reinforcement of the concepts.
Summaries are useful in text review, especially in preparing for exams.
At the end of each chapter, the student is asked to create a CONCEPT MAP
. Concept maps grew out of the constructivist
movement in education, which asserts that student learning is most effective when
new information confronts previous understanding. The concept map provides a
powerful method for resolving such confrontation and for visualizing concept
integration.
