Choosing an Experimental Organism The organism should be small. The organism should produce many progeny. The life cycle should be short The organism should have a small genome. The organism should be developmentally complex. Accumulated knowledge is essential
Choosing an Experimental Organism • The organism should be small. • The organism should produce many progeny. • The life cycle should be short. • The organism should have a small genome. • The organism should be developmentally complex. • Accumulated knowledge is essential
Mendelian genetics Who was Gregor Mendel? What were Mendels experiments? How did mendel derive his rules? How do geneticists diagram crosses? What are the rules of probability geneticists use? What can we learn from pedigree analysis?
Mendelian Genetics • Who was Gregor Mendel? • What were Mendel’s experiments? • How did Mendel derive his rules? • How do geneticists diagram crosses? • What are the rules of probability geneticists use? • What can we learn from pedigree analysis?
he Mc Graw-Hill Comp nc Permission required for reproduction or display Experiments with garden peas Cross- fertilization: ollen Stigma transferred Anthers dusted onto removed stigma of previously recipient Anthers Seed () formation (♀) Seed Ovules germination within ovary
Mendel performed simple crosses Parent generation P1X P2 First Filial generation Second Filial generation n each generation he recorded the phenotype of each individual and the number with each phenotype
Mendel performed simple crosses • Parent generation P1 X P2 • First Filial generation F1 • Second Filial generation F2 • In each generation he recorded the phenotype of each individual and the number with each phenotype
Mendels first observation Alleles show dominance Dominance: One allele controls the phenotype Dominant phenotype is given by two genotypes Homozygote and heterozygote: RR and Rr Recessive phenotype is given by one phenotype Homozygote: rr
• Dominance: One allele controls the phenotype. • Dominant phenotype is given by two genotypes: Homozygote and heterozygote: RR and Rr • Recessive phenotype is given by one phenotype: Homozygote:rr Mendel’s first observation: Alleles show dominance