Preparatory Mindset

Study this chapter with focus on how genetic principles affect clinical practice.

Core Concepts

• Birth defects: Structural or functional abnormalities present at birth. Most occur in embryonic period (weeks 3-8).


• Deformation: Mechanical forces causing abnormal development (e.g., oligohydramnios → clubfoot)


• Disruption: Breakdown of previously normal tissue (e.g., amniotic band syndrome)


• Malformation: Intrinsic abnormality in development (e.g., Greig cephalopolysyndactyly)


• Dysplasia: Abnormal organization of cells into tissues (e.g., skeletal dysplasias)


• Major birth defects: Affect 2-3% of live births. Leading cause of infant mortality.


• Apoptosis: Programmed cell death — critical for normal development (e.g., digit separation)

High-Yield Points

• Most birth defects occur in embryonic period (3-8 weeks gestation)


• Malformation = intrinsic; Deformation = mechanical; Disruption = breakdown of normal tissue


• Apoptosis is essential for normal development

Topic Summary

Developmental genetics explains how genes guide embryonic development and what happens when this goes wrong.