Principles of Genetics

Citation

Snustad, D. P., & Simmons, M. J. (2015). Principles of Genetics (7th ed., loose-leaf). John Wiley & Sons.

Chapter Summary

The seventh edition (October 2015, 648 pages) has twenty chapters in print, with answers to odd-numbered questions, a glossary and an index, and four further chapters (21–24) available online. Chapters open with a short topical story, such as the Dolly cloning story in Chapter 2 or the Denisova Cave genomes in Chapter 15, and the contents show recurring "Solve It" and "Problem-Solving Skills" boxes inside the chapters. The publisher presents the book as a popular text for the introductory course, with a human emphasis, and says this edition was updated and streamlined to focus on key concepts and principles.

Chapter 1: The Science of Genetics

An opening survey. It names three milestones (Mendel's rules of inheritance, the structure of DNA, and the Human Genome Project), introduces DNA as genetic material, replication, gene expression and mutation, and outlines the levels of genetic analysis (classical, molecular, population) and applications in agriculture, medicine and society.

Chapter 2: Cellular Reproduction

Cells and chromosomes, mitosis and meiosis, and the life cycles of three model organisms: baker's yeast, Arabidopsis and the mouse.

Chapters 3–4: Mendelism: The Basic Principles of Inheritance; Extensions of Mendelism

Chapter 3 covers Mendel's pea experiments, monohybrid and dihybrid crosses, the Punnett square, forked-line and probability methods, the chi-square test and pedigrees in human genetics. Chapter 4 extends these ideas to incomplete dominance, multiple alleles, environmental effects, penetrance and expressivity, epistasis, pleiotropy and inbreeding.

Chapters 5–7: The Chromosomal Basis of Mendelism; Variation in Chromosome Number and Structure; Linkage, Crossing Over, and Chromosome Mapping in Eukaryotes

Chapter 5 links genes to chromosomes through nondisjunction, sex linkage in humans, sex determination and dosage compensation. Chapter 6 treats polyploidy, aneuploidy, deletions, duplications, inversions and translocations. Chapter 7 covers linkage, recombination, crossing over, two- and three-point mapping, cytogenetic mapping and linkage analysis in humans.

Chapter 8: The Genetics of Bacteria and Their Viruses

Bacteriophage T4 and lambda, mutants in bacteria and the mechanisms of gene exchange: transformation, conjugation, plasmids and episomes, and transduction.

Chapters 9–10: DNA and the Molecular Structure of Chromosomes; Replication of DNA and Chromosomes

Chapter 9 starts from the proof that DNA carries genetic information, then covers the structures of DNA and RNA, chromosome structure in viruses, prokaryotes and eukaryotes, nucleosomes, centromeres and telomeres. Chapter 10 presents semiconservative replication, replication forks, the prokaryotic replication machinery, and eukaryotic features including telomerase.

Chapters 11–12: Transcription and RNA Processing; Translation and the Genetic Code

Chapter 11 covers the central dogma, transcription in prokaryotes and eukaryotes, capping and polyadenylation, introns and splicing. Chapter 12 moves through protein structure, the one gene–one enzyme experiments, ribosomes, tRNAs, the stages of polypeptide synthesis and the properties of the genetic code, including the wobble hypothesis.

Chapter 13: Mutation, DNA Repair, and Recombination

Types and molecular bases of mutation, mutagenesis (including the Ames test), the complementation test, DNA repair mechanisms and human repair-deficiency diseases, and recombination, including gene conversion.

Chapters 14–16: The Techniques of Molecular Genetics; Genomics; Applications of Molecular Genetics

Chapter 14 covers cloning, restriction enzymes, PCR, libraries, blotting methods and DNA sequencing. Chapter 15 covers genomics, genome maps, the Human Genome Project, SNPs, microarrays, and prokaryotic and eukaryotic genomes. Chapter 16 turns to gene identification and diagnosis, gene therapy, DNA profiling, transgenic organisms, reverse genetics, RNA interference and genome engineering with CRISPR/Cas9.

Chapters 17–18: Regulation of Gene Expression in Prokaryotes; Regulation of Gene Expression in Eukaryotes

Chapter 17 covers operons, the lac and trp operons and posttranscriptional regulation. Chapter 18 covers transcription factors, RNA interference, chromatin organisation, DNA methylation, imprinting and whole-chromosome inactivation.

Chapters 19–20: Inheritance of Complex Traits; Population Genetics

Chapter 19 treats quantitative traits, variance, heritability, quantitative trait loci, genome-wide association studies and correlations between relatives. Chapter 20 treats allele frequencies, the Hardy–Weinberg principle, natural selection, genetic drift and equilibrium.

Online Chapters 21–24

Chapter 21, "Transposable Genetic Elements", Chapter 22, "The Genetic Control of Animal Development", Chapter 23, "The Genetic Basis of Cancer" and Chapter 24, "Evolutionary Genetics" are listed in the contents with their own "WC" page numbering.

Key Concepts

Chapters 1–8: Transmission genetics

• Segregation and independent assortment: Mendel's principles, tested with the chi-square method.
• Epistasis and pleiotropy: gene interactions in Chapter 4.
• Linkage and mapping: crossing over as the basis of genetic maps.
• Nondisjunction: evidence for the chromosome theory.

Chapters 9–16: Molecular genetics

• Semiconservative replication: the replication mode of DNA.
• Central dogma, splicing and the genetic code: Chapters 11 and 12.
• DNA repair and complementation: Chapter 13.
• Cloning, PCR and CRISPR/Cas9: tools and applications.

Chapters 17–20: Regulation and populations

• Operons: the lac and trp systems.
• Heritability and QTL: the analysis of complex traits.
• Hardy–Weinberg principle: the baseline for allele frequencies.

Critical Analysis

Strengths

• Full path from Mendel to genomics. The contents run from crosses and chromosomes, through DNA, gene expression and techniques, to genomics, complex traits and populations.
• Practice built into the chapters. The "Solve It" and "Problem-Solving Skills" boxes appear throughout, including topics such as counting chromosomes, predicting from pedigrees and mapping genes, and the publisher emphasises analysis of experimental data.
• Human emphasis. The publisher stresses the human perspective, and the contents include genetic counseling, human linkage, inherited repair diseases, gene therapy and DNA profiling.
• Streamlined. The publisher says the book is comprehensive but not encyclopedic and that topics were eliminated or simplified in this edition.

Limitations

• Some topics are online only. Transposable elements, animal development, cancer and evolutionary genetics are in online chapters.
• Short treatment of the later topics. Population genetics occupies one chapter of about twenty pages (Chapter 20), and complex traits one chapter (Chapter 19), so readers who need depth there will want a dedicated text.

Where It Fits in the Course

This is a mid-level genetics text that goes from classical genetics to molecular and population genetics. Genes: A Very Short Introduction and Introducing Genetics: From Mendel to Molecules are shorter books for a first encounter. Introduction to Genetic Analysis is a comparable text that connects classical inheritance with molecular mechanisms and genomic analysis, aimed at students who want practice interpreting crosses and maps, and the choice between the two is largely one of style and problem sets. Genomes 5 goes much further into whole genomes than Chapter 15 here, and Principles of Population Genetics is the standard text to follow Chapter 20 for readers who want the theory of allele frequencies in depth.

How to Use This Book

It is written for students taking an introductory genetics course after introductory biology. Read Chapters 1–8 for transmission genetics, 9–13 for the molecular basis, and 14–18 for tools and regulation; Chapters 19–20 are the quantitative end. For a course with a molecular emphasis, Chapters 3–7 can be read faster. Work the "Solve It" boxes as you go, and treat the end-of-chapter problems (with answers to odd-numbered ones at the back) as the main way to learn crosses, mapping and probability.