This Guide offers an accessible overview of HL genetics, a core component of the IBDP Biology HL syllabus. Building from the basics, it will equip you with the understandings, applications, and skills needed to solve more challenging problems. Coverage includes symbols, phenotypes, and genotypes; multiple alleles and codominance; sex chromosomes and sex linkage; autosomal linkage and crossing over; and recombinants. Key features: concise definitions of important concepts and terms; clearly labelled diagrams that are easy to reproduce in exams; key point boxes summarise essential information; and short answer and multiple-choice questions to test your understanding