Chapter 4, Heredity and Evolution Genetic Principles Discovered by Mendel Mendelian Inheritance in Humans Non-Mendelian Patterns of Inheritance Modern Evolutionary History Definition of Evolution Factors that Produce and Redistribute Variation Review of Genetic and Environmental Factors

Mendel’s Discoveries Segregation Dominance and Recessiveness Independent Assortment

Principle of Segregation gamete production Members of each gene pair separate so each gamete contains one member of a pair. fertilization Full number of chromosomes is restored and members of gene pairs are reunited.

Mendelian Inheritance in Humans Over 4,500 human trains are known to be inherited according to simple Mendelian principles. The human ABO blood system is an example of a simple Mendelian inheritance.

Inherited Genetic Disorders Dominant disorders are inherited when one copy of a dominant allele is present. Recessive disorders require the presence of two copies of the recessive allele. Recessive conditions: cystic fibrosis, Tay-Sachs disease, sickle cell anemia, and albinism.

Non-Mendelian Patterns of Inheritance: Polygenic Polygenic traits are influenced by genes at two or more loci. Continuous traits have a series of measurable intermediate forms between the two extremes. Examples: skin color, stature, eye color.

Non-Mendelian Patterns of Inheritance: Pleiotropy A single gene influences more than one phenotype expression. The rule rather than the exception. Example: sick-cell anemia, PKU.

Modern Evolutionary Theory Evolution is a two-stage process: Production and distribution of variation. Natural selection acting on this variation.

Factors That Produce and Redistribute Variation mutation gene flow genetic drift recombination