Genetics Gregor Mendel Father of Genetics 1866 published
Genetics
Gregor Mendel § “Father of Genetics” § 1866 - published findings on plant breeding and inheritance (During American Civil War) § Not discovered until early 1900 s
Keys to Success § Used “True-Breeding” pea plants (“purebreds”) § Always produce offspring with only one form of a trait § Studied only 1 characteristic at a time § Analyzed data mathematically
Pea Plant Reproduction 1. Self-pollination § Pollen fertilizes egg cells on same flower § 1 parent 2. Cross-pollination § Pollen from flower of one plant fertilizes egg cells on another plant § 2 parents
§ Mendel controlled breeding by crosspollinating § To prevent self-pollination, Mendel removed male parts from a flower and dusted the flower with pollen from a different pea plant
Genetics: § The science of heredity Heredity: § The biological inheritance of traits from parent to offspring
Genetics used for: 1. Preventing & treating diseases 2. Developing tougher plants to increase food production
Generations 1. P generation: parent generation § “true - breeding” 2. F 1 generation § First generation of offspring 3. F 2 generation § Second generation produced when f 1 generations are crossed
Allele § The different forms of a gene § 2, 3, or even 12 possible alleles per gene
Dominant § Form of the gene that is expressed § Capital letter: T
Recessive § Form of a gene (allele) that is only expressed in homozygous state § Lowercase letter: t
Homozygous § 2 identical alleles for the same trait § Homozygous dominant: TT § Homozygous recessive: tt
Heterozygous § 2 different alleles for the same trait § Tt : dominant trait will be expressed § Also called a “hybrid”
Genotype § Genetic make-up of an organism § The “letters” § Tt or TT or tt § Aa or AA or aa
Phenotype § Physical expression of a trait § Ex: Tall or Short
Examples: TT = genotype Tall = phenotype tt = genotype Short = phenotype
Law of segregation § The two alleles for each trait separate during meiosis § So, for each gene, an organism receives one allele from each parent - during fertilization
Part 2
Monohybrid cross § Use a Punnett square to cross 2 hybrids: Yy x Yy § What are the possible genotypes? § What is the genotypic ratio? § What is the phenotypic ratio?
Seed Color § P generation cross: (“true - breeding”) § Yellow peas x Green peas § F 1 generation: § All yellow § F 2 generation: § 6022 yellow : 2001 green § 3 yellow : 1 green
Dihybrid cross § A Special type of two - factor cross Yy. Rr x Yy. Rr (heterozygous for both traits) § You will always find the same phenotypic ratio. What is this ratio?
Law of Independent Assortment § Genes on separate chromosomes sort independently during meiosis § Alleles for seed shape separate independently from seed color alleles § So, seed shape is not connected to seed color
- Slides: 28