Patterns of Heredity and Human Genetics Chapter 12

Pedigree A graphic representation of genetic inheritance Circle = female Square = male Shaded = exhibits trait Half-shaded = carrier of trait Carrier – heterozygous individual

Horizontal line = parents or mates Vertical line = offspring Each row = a generation

Simple Recessive Heredity Most genetic disorders are caused by recessive alleles Cystic fibrosis – formation and accumulation of thick mucus in lungs and digestive tract Tay-Sachs Disease – deterioration of mental abilities because of accumulation of lipids in nervous system Phenylketonuria – damage to nervous system due to phenylalanine

Simple Dominant Heredity Examples Cleft chin Widow’s peak Hitchhikers thumb Almond-shaped eyes Huntington’s disease – results in break down of certain areas of the brain

Complex Patterns of Inheritance Incomplete dominance – get intermediates (blending) Codominance – both alleles are expressed Multiple alleles-ABO blood type