BIOB 110cs 1st Edition Lecture 20 Genetics and Inheritance Early Ideas Creationism many societies believed in this all creatures are the result of God and his plans Spontaneous generation medieval and later scientists believed that creatures would arise randomly o Mice would be made in 21 days if a dirty rag was placed in a barrel with some grain or other food Early Observations Anton Von Leeuwenhock 1660s was the first to use a microscope to examine living organisms and soon discovered what he called animalcules and began the Cell Theory Proformationists believed that the egg or sperm contained a preformed miniature human since they believed to see a human face in sperm cell Jean Lamark 1780s Lamarkism inheritance of aquired traits He believed that if a giraffe needed to reach higher food it would stretch its neck and the offspring would have longer necks due to the stretching Louis Pasteur 1860 debunked the idea of spontaneous generation by putting sterile cultures in a closed container and some in an open container Showed that mold and other growth did not just appear but came from things people touched and the surroundings Charles Lyell 1860s he was a geologist and found that small changes over time do have a lasting and profound effect Charles Darwin and Alfred Wallace 1859 natural variation exists and the variation is heritable o Inheritance works because competition for resources is intense Malthusian and that natural selection favors those that are well adapted survival of the fittest Gregor Mendel 1860s The Father of Modern Genetics Prior to his studies o 100 years prior tobacco hybrids were made and disproved Lamark s idea of blending inheritance o In successive generations pea plants showed segregation of traits Working with pea plants advantages o True breeding varieties exist o Making hybrids is possible o They germinate quickly o Easy to make self and cross fertilizations Easy to measure traits o He crossed purple and white flowers and the offspring F1 generation were purple so purple is a dominant trait and white is a recessive trait for these flowers o In the second generation F2 3 4 flowers were purple and the rest were white o Dominant recessive ratio was 3 1 o The key to this discovery was making lots of crosses and counting the offspring Model of Inheritance o Factors were dominant P or recessive p o Each offspring received one factor form each parent o Different factors can control the same trait o Different factors for the same trait remain discrete no blending o Only the dominant factor is expressed o Segregation of traits in succeeding generations is called Mendel s First Law of Heredity The Law of Segregation o This is also applicable for animal and plant breeding Mendel s terms and modern terms o Factor allele one of several possible forms of a gene o Trait phenotype observable form of a trait o PP genotype genetic basis of the phenotype Most early biochemists thought proteins were genetic molecules in 1952 this was proved wrong Pea plants Gene location is the locus If both alleles are the same it is homozygous If the alleles are different it is heterozygous PP homozygous dominant purple Pp heterozygous dominant purple Pp homozygous recessive white