9.8 Genetic traits in humans can be tracked through family pedigrees
9.9 CONNECTION: Many inherited traits in humans are controlled by a single gene
Because a trait is dominant does not mean that it is
• “normal” or
• more common than a recessive trait.
Wild‐type traits are
• those most often seen in nature and
• not necessarily specified by dominant alleles.
Some autosomal disorders in humans (see next slide)
Recessive Disorders
• Most human genetic disorders are recessive
Dominant Disorders
• Fewer human genetic disorders are dominant
Achondroplasia (軟骨發育不全症)
- Homozygous dominant genotype dies during embryo
- Heterozygotes survive
- One form of dwarfism
- Head and torso develop normally, but not arms and legs.