Gregor Mendel “The Father of Genetics” Chapter 10, Sections 1 and 2

Gregor Mendel (1822-1884) An Austrian monk who used a scientific approach to study inheritance, giving birth to GENETICS (the study of heredity) There was no knowledge of genes or DNA at the time; Therefore, Mendel’s refers to “factors” (today called genes) His success, in part, came from his choice to use pea plants in his study Contrasting traits or characteristics Reproduce sexually, quickly, and have many offspring Accessible and easy to handle

Controlled Reproduction Stamen(♂) produces pollen Carpel(♀) produces ovules (eggs) Removing immature stamen prevents self-fertilization

Mendel’s 7 Traits of Pea Plants

In The Garden… Mendel identified stocks of plants that were TRUE-BREEDING for a particular trait Tall Plant  self-fertilization  All Tall Offspring Mendel cross-fertilized two true-breeding plants with contrasting characteristics (ex: purple flowers and white flowers) He called them the P generation (for Parental) What do you think the offspring looked like?

He called the F1 generation HYBRIDS Mendel’s F1 Generation F1 (for Filial) or “son” in Latin! The offspring were 100% Purple Flowering Mendel repeated this experiment and observed similar results with all 7 of the traits he studied! He called the F1 generation HYBRIDS

A Second Generation Mendel let the F1 generation self-fertilize and created a F2 generation The white-flowering trait reappeared in the 2nd Generation!! (3 Purple to 1 White)

Mendel’s Principles (in modern terms) There are different forms of genes called alleles Ex: Gene: height Alleles: tall, dwarf Genes are inherited in pairs, one allele from each parent Homozygous: identical alleles Heterozygous: different alleles In a hybrid, only the dominant allele (T) will be expressed (or seen). The other allele is recessive (t). Alleles segregate (separate) from each other during gamete formation and rejoin during fertilization to make the offspring

Principle of Segregation What process segregates the alleles during gamete formation???

MEIOSIS!!

Punnett Squares A diagram that can be used to show the potential outcome of a genetic cross

Genotype and Phenotype Organisms with the same PHENOTYPE (physical appearance) may not have the same GENOTYPE (genetic make-up) Purple Flowers (PP) Purple Flowers (Pp) How do you determine the genotype of an organism with a dominant trait?

Test Cross Cross the dominant (unknown genotype) with the recessive (known genotype) 50% Green 50% Yellow 100% Green

Mendel’s Principle of Independent Assortment Mendel also looked at two-factor crosses or DIHYBRID crosses Traits sort independently from one another during gamete formation

Mendel’s F1 and F2 Two-Factor Cross