Gregor Mendel & Punnett Squares Genetic Continuity

Quick Reminders... Homozygous: an individual with identical alleles at a specific loci (i.e. RR or rr) Heterozygous: an individual with two different alleles at a specific loci (i.e. Rr) Dominant: expressed in the heterozygous condition Recessive: not expressed in the heterozygous condition Genotype: the unobservable genetic make-up of an organism (i.e. The code that expresses the observable traits) Phenotype: the observable traits of an organism (i.e what you can see)

Gregor Mendel ( ) Born Johann Mendel,Austria (1822) Admitted to Augustinian Monastery of St. Thomas in Brno (1843) Studied physics and botany at the University of Vienna ( ) Taught physics and natural science for 16 years, Brno (1854) Research phase , when he was elected Abbot of the monastery

Gregor Mendel Died of a kidney disorder (1884) “His death deprives the poor of a benefactor, and mankind at large of a man of the noblest character, one who was a warm friend, a promoter of the natural sciences, and an exemplary priest.”

“Father of Genetics” (since 1866) Opened our minds to inheritance Performed hybridization experiments with pure breeding garden pea plants Why did he choose the pea plant? Mendel followed 7 visible features with contrasting traits

Mendel took two pure breeding individuals (i.e. He developed a group of plants which only demonstrated the purple when crossed with one another. A second group of plants only demonstrated the white trait when crossed with one another) and mated them to create the first filial generation (F 1 generation) Pea Plant Parentals (P 1 generation)

Monohybrid Crosses F 1 Generation Genotype Ratio: 0:4:1 Phenotype ration: 4:0 F 2 Generation Genotype Ratio: 1:2:1 Phenotype Ratio: 3:1

Mendel’s First Three Postulates (Principles of Inheritance) 1. Genetic characteristics are controlled by unit factors (alleles) that exist in pairs in individual organisms -Three possible combinations because there are two types of alleles (i.e. HH, Hh, hh) 2. When two unlike unit factors (alleles) responsible for a single character are present in a single individual, one unit factor is dominant over the other, which is said to be recessive -i.e. “H” is dominant over “h” -Dominant and recessive also refer to designated traits (i.e. Tall stems are dominant over dwarf stems) 3. During the formation of gametes, the paired unit factors separate or segregate randomly so that each gamete receives on or the other with equal likelihood - i.e. If your father is heterozygous for height (has a tall allele a short allele), you have a 50% chance of getting either one

Test Cross: F 2 Generation

Dihybrid Crosses Passing on more than one characteristic at a time Genotypic Ratio: 1:2:2:1:4:1:2:2:1 Phenotypic Ratio: 9:3:3:1

Mendel’s Fourth Postulate 4.Independent Assortment: during gamete formation, segregating pairs of unit factors assort independently of each other (i.e. Whether a plant will have a green or yellow seed is not at all influenced by whether it will be wrinkled or round)