3 11.1 The Work of Gregor Mendel Every organism has an inherited set of characteristics from their parent or parents. These are our genes.Genetics is the study of heredity.
4 Genetics Passing of genes from parent to offspring Asexual reproduction: One parentLow diversityEssentially mitosisSexual reproduction: Two parentsHigh diversityMixes up DNA through meiosis
5 Gregor Mendel Father of genetics Austrian monk born in 1822 A priest who studied science an mathematicsWorked at a monastery and taught high school
6 Gregor mendelCarried out a series of experiments in the monastery’s gardenObserved fertilization process of garden peas
7 Mendel’s first experiment Crossbred truebreeding plantsTruebred – an organism who produce identical offspring to themselvesObserved 7 traits in offspringTrait: A specific characteristic that varies based on what genes are inherited.
8 Sexual reproduction in plants Pea flowers are normally self-pollinating, which means that sperm cells in pollen fertilize the egg cells in the same flower. The seeds then grow plants with the same characteristics as the single parent.Mendel wanted to produce seeds via cross-pollination (joining male and female reproductive cells from two different plants.)
9 Mendel accomplished cross-pollination by cutting away the pollen-bearing male parts & then dusting pollen from another plant onto the flower.This process produced seeds that had two different plants as parents. This made it possible for Mendel to cross-breed plants with different characteristics, and study the results.
10 Mendels’s first experiment P: Parent generationCross 2 truebredsF1: Filial 1 generationProduced hybrids: Resulting offspring from two truebred parents with different traitsNext, cross-fertilized hybrids from F1 generationF2: Filial 2 generation
11 Mendel’s conclusionsBiological inheritance is determined by “factors” that are passed from one generation to the next.Principle of dominance: states that some alleles are dominant and others are recessive.
12 What we call “factors” today Genes are the chemical factors that determine traits.The different forms of a gene are called alleles.Genes are located in specific positions on chromosomes.
13 Mendel’s conclusionsMendel had one more question remaining about his crosses… What happened to the alleles that disappeared? Ex: Cross a Tall and a Short plant and all of the F1 offspring were tall.When Mendel allowed the F1 generation to self pollinate, he was shocked to see the missing alleles reappear.
14 Principles of Dominance Section 11-1P GenerationF1 GenerationF2 GenerationTallShortTallTallTallTallTallShort
15 Principles of Dominance Section 11-1P GenerationF1 GenerationF2 GenerationTallShortTallTallTallTallTallShort
16 Principles of Dominance Section 11-1P GenerationF1 GenerationF2 GenerationTallShort
17 Law of segregationMendel correctly assumed that the allele for shortness was masked by the dominant tall allele, but was still puzzled on why it showed up again in the F2.He knew that the short allele must have separated or SEGREGATED from the tall allele at some point.Mendel again correctly hypothesized that this segregation may have happened during sex cell or gamete formation.During gamete formation, alleles segregate so that each gamete carries a single copy of each gene.