Introducing Genetics: From Mendel to Molecules

Citation

Thomas, A. (2014). Introducing Genetics: From Mendel to Molecules (2nd ed.). Garland Science.

Chapter Summary

The second edition runs to about 260 pages in thirteen chapters, followed by solutions to the problems, an appendix, a glossary, further reading and an index. Its order is the traditional "Mendel first" sequence the subtitle announces: eight chapters on Mendelian inheritance and chromosomes, two on quantitative and population genetics, and three on the molecular basis of heredity. The publisher notes that examples come from insects, plants, animals and humans, and that every chapter ends with problems. A review of the first edition (2003), which had the same thirteen-chapter plan, adds that each chapter closes with a summary before the problems.

Chapter 1: Introduction

A short opening chapter (six pages) on the origins of genetics and its key ideas. The publisher's description says it begins with a brief look at how far the science progressed during the twentieth century.

Chapters 2–4: Monohybrid Inheritance; Extensions to Monohybrid Inheritance; Dihybrid Inheritance

These three chapters, about fifty pages together, build Mendelian analysis step by step: single-gene crosses, then the variations on them (the first-edition review names incomplete dominance and co-dominance), then two-gene crosses. The same review notes the test cross and the chi-square test, and a section on complementary genes illustrated with petal colour in sweet peas.

Chapter 5: The Chromosomal Basis of Inheritance

This chapter connects Mendel's factors to chromosomes. In the first edition it described mitosis and meiosis in some depth and then revisited the laws of segregation and independent assortment in chromosomal terms.

Chapters 6–7: Sex Determination and Sex Linkage; Linkage and Chromosome Mapping

Chapter 6 covers sex chromosomes, their role in determining sex, and the inheritance of sex-linked traits. Chapter 7 deals with genes on the same chromosome and how crossover frequencies are used to map them; the first-edition review mentions crosses, pedigrees and the test cross in linkage studies.

Chapter 8: Variation in Chromosomal Number and Structure

Chromosome abnormalities are treated from two sides: how they arise in cell division and what their genetic and phenotypic consequences are. Changes in chromosome number come first, then changes in structure, with plant and human cases.

Chapter 9: The Principles of Quantitative Genetics

The first of two chapters on traits and populations rather than single crosses. It explains why many traits do not follow simple Mendelian patterns. The first-edition review praised its engaging opening scenario (a farmer moving his prize potatoes from the Andes to Patagonia) and its simple, logical progression from a mean to the analysis of multifactorial traits.

Chapter 10: An Introduction to Population Genetics

The chapter introduces allele and genotype frequencies, the Hardy–Weinberg law and its derivation from Mendelian principles, testing for equilibrium, and the forces that disturb it: mutation, migration, genetic drift and selection, according to the first-edition review, which notes graphs, photographs and case studies for each.

Chapters 11–12: Heredity at the Molecular Level; From Genes to Proteins

The molecular part of the book. Chapter 11 covers DNA, its structure and replication; Chapter 12 (about twenty pages) follows the path from gene to protein through transcription and translation. In the first edition the section ended with types of mutation, illustrated by xeroderma pigmentosum and sickle cell anaemia.

Chapter 13: Manipulating DNA

The final chapter introduces the techniques of recombinant DNA and gene manipulation and their uses in medical and plant biotechnology. The publisher describes it as covering the techniques behind the current genetic revolution. In the first edition it included a table of the benefits and risks of genetically modified crops.

Key Concepts

Chapters 1–4: Mendelian analysis

• Monohybrid and dihybrid crosses: following one or two genes through generations to infer how they are inherited.
• Incomplete dominance and co-dominance: departures from simple dominance in which heterozygotes show intermediate or both phenotypes.
• Test cross: crossing with a homozygous recessive to reveal an individual's genotype.
• Chi-square test: checking whether observed offspring ratios fit expected ones.

Chapters 5–8: chromosomes

• Chromosome theory of inheritance: genes are carried on chromosomes, whose behaviour in meiosis explains Mendel's laws.
• Sex linkage: inheritance patterns of genes on the sex chromosomes.
• Linkage and chromosome mapping: using recombination between genes on one chromosome to estimate their relative positions.
• Chromosomal aberrations: changes in chromosome number or structure and their consequences.

Chapters 9–10: quantitative and population genetics

• Quantitative traits: characteristics that vary continuously and depend on several genes and the environment.
• Hardy–Weinberg equilibrium: the expected genotype frequencies in a population that is not evolving.
• Disturbing forces: mutation, migration, genetic drift and selection.

Chapters 11–13: molecular genetics

• DNA replication: the copying of the genetic material.
• Transcription and translation: the two steps from a gene to its protein.
• Recombinant DNA: combining DNA from different sources to clone genes and modify organisms.

Critical Analysis

Strengths

• Clear and well illustrated. The 2004 Heredity review of the first edition called the approach lucid and clear and said real-life examples, charts and photographs clarify derivations. Reviews of the second edition quoted by the publisher, from The Biochemist (April 2015) and a genetics journal (July 2015), praise its succinctness, its well-annotated figures and its glossary, and recommend it for readers with little or no prior knowledge.
• Problems with solutions. Every chapter ends with problems, and solutions occupy a section of about twenty pages at the back, which makes the book usable for self-study and for checking answers before an exam.
• Proportions suited to a first course. Over half the book goes to transmission genetics and chromosomes, the material students most often struggle with in a first genetics module, and quantitative and population genetics each receive a full chapter, which very short introductions often omit.
• Broad range of organisms. Examples come from insects, plants, animals and humans, so the book is not limited to human or medical genetics.

Limitations

• Simplified molecular biology and biotechnology. The first-edition review judged the gene-manipulation chapter well written but too simple to convey the complexity of genetic engineering, and singled out a claim about livestock as "biofactories" as overstated. Only three chapters cover molecular genetics, without separate treatment of gene regulation or genomics.
• Dated in its molecular chapters. The second edition dates from 2014. Developments since then, in genome editing and sequencing above all, are outside the book.
• Introductory depth throughout. Quantitative and population genetics are introduced in about twenty pages each; students taking population genetics further will need a specialist text.

Where It Fits in the Course

In the genetics course list this is the first textbook to read. It is more demanding than Jonathan Slack's Genes: A Very Short Introduction, a non-technical essay on what "gene" means in molecular biology, population studies and evolution, because it teaches the methods (crosses, chi-square, mapping, Hardy–Weinberg) and gives problems; read Slack for the concepts and Thomas to learn to work with them.

Thomas also prepares students for the two comprehensive main texts. Griffiths and colleagues' Introduction to Genetic Analysis connects classical inheritance with molecular mechanisms and modern genomics and is taught through problem solving, and Snustad and Simmons's Principles of Genetics covers classical and molecular genetics, genomics and biotechnology in depth. Either can follow Thomas, or Thomas can be used alongside them to consolidate the Mendelian chapters. Chapter 10 is a first step towards Hartl and Clark's Principles of Population Genetics, and Chapters 11–13 towards Terry Brown's whole-genome treatment in Genomes 5.

How to Use This Book

The book is written for students meeting genetics at university for the first time, including those on courses outside the life sciences, and for health professionals who need a grounding. School biology is enough; the mathematics is basic arithmetic, probability and the chi-square test.

A practical plan:

• Core, in order: Chapters 2–7. Each chapter builds on the crosses of the previous one, and working the end-of-chapter problems before moving on is the main way to learn this material. Try each problem before looking at the solutions at the back.
• Next: Chapter 8 on chromosome abnormalities, then Chapters 9–10 on quantitative and population genetics. These can be postponed if the course covers them later, but Chapter 10 is worth reading before any evolution module.
• Molecular chapters: Chapters 11–13 are short. Students who already know molecular biology can skim them; others should read them and then follow up with a molecular biology textbook for gene regulation and modern techniques.
• Reference: use the glossary while reading other genetics texts, and the further reading list for next steps.

Pair the book with lecture problem sets or the larger problem collections in Griffiths, and check Chapter 13 against a current source on genome editing.