Patterns of Inheritance
Historical Roots
• Ancient greeks– Hippocrates
• Pangenesis
– Aristotle• Potential for features, not actual particles of features
themselves
Gregor Mendel
• Austrian Monk (1800’s)
• Mathematician
• Heritable factors
• Peas
Mendel’s 4 Theories
• Alternate forms of genes exist (Alleles)
• 2 genes per trait
• Gamete only carries one allele
• Dominance vs. Recessive
Independent Assortment
Mendel Got Lucky
• Incomplete Dominance
• Multiple Alleles
• Pleiotropy
• Polygenic inheritance
• Linkage
Incomplete Dominance
RR Rr rr
Polygenic Inheritance
Linkage• Perturbs mendle’s ratios of dihybrid cross
• Genes located close together on chromosome
• Chromosomes determine sex in many species, not just humans
• Sex chromosomes carry some other genes– Sex linked– Some diseases have sex linkage component