Preparatory Mindset

Genetics is the foundation of modern medicine. This chapter establishes the vocabulary and conceptual framework. Focus on definitions: the difference between cytogenetics and molecular genetics, and what each contributes to patient care.

Core Concepts

• Genetics: Study of variation and heredity in living organisms


• Medical Genetics: Application of genetics to human health and disease


• Cytogenetics: Branch studying chromosomes — their structure, number, and abnormalities visible microscopically


• Clinical Cytogenetics: Application of chromosome studies to clinical medicine (diagnosis, prognosis, counseling)


• Chromosome Disorder: Disorders caused by numerical or structural chromosome abnormalities


• Karyotype: Ordered display of chromosomes by size, centromere position, and banding pattern


• Metaphase: Cell cycle stage where chromosomes are most condensed → best for visualization


• Neoplasia: Abnormal cell proliferation; many cancers have cytogenetic abnormalities


• Polymorphism: DNA sequence variant present in >1% of population, usually without direct disease effect

High-Yield Points

• Cytogenetics = chromosomes (microscope level); Molecular genetics = DNA (sequence level)


• Karyotype requires metaphase-arrested cells (colcemid treatment)


• Polymorphism ≠ disease mutation — frequency >1% in population

Topic Summary

Medical genetics bridges chromosome-level (cytogenetics) and DNA-level (molecular) analysis. The karyotype is the fundamental tool for visualizing chromosomes.