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 Traits

Generations

Mendel’s 4 Theories

• Alternate forms of genes exist (Alleles)

• 2 genes per trait

• Gamete only carries one allele

• Dominance vs. Recessive

Independent Assortment

Testcross

Probability

Mendel Got Lucky

• Incomplete Dominance

• Multiple Alleles

• Pleiotropy

• Polygenic inheritance

• Linkage

Incomplete Dominance

RR Rr rr

Multiple Alleles

Pleiotropy

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