The Work of Gregor Mendel SECTION 11.1
Experiments of Gregor Mendel
u Heredity
u Set of characteristics that are passed from a parent to their offspring
u Genetics
u Scientific study of heredity.
u Gregor Mendel
u Austrian monk who studied science and mathematics at the University of Vienna.
u Worked in a monastery/high school teacher and tended the monastery garden.
Mendel's Work with Garden Peas u Mendel studied the flowers and became familiar
with their anatomy.
u Garden peas reproduce sexually, so he was able to control when and where “fertilization” (joining of the reproductive cells) occurs.
u Mendels plants were considered “true-breeding” which means they self-pollinate and produce offspring identical to themselves.
u All characteristics (traits) would be the same.
u He studied 7 different contrasting traits and crossed the plants to produce plants that are considered “hybrids” or offspring with characteristics from both parents.
Genes & Alleles u Genetic Crosses
u P = Parental Generation u F1 (first filial generation) = offspring of P generation u Mendel discovered that all of the F1 offspring from
his initial crosses had the characteristic of ONLY one parent.
u He formed 2 conclusions: u An individuals characteristics are determined by
factors that are passed from one parental generation to the next. These factors are called “genes”.
u Some “alleles” (forms of a gene) are dominant and others are recessive. This is referred to as the Principle of Dominance.
u Organisms with at least one dominant gene will exhibit that trait.
u Organisms with a recessive allele will ONLY show that trait if NO DOMINANT ALLELE IS PRESENT.
Segregation u Mendel also wondered if the recessive
alleles had simply disappeared or were they still present in the new plants (offspring).
u To find out, he allowed the F1 plants to self pollinate and produce offspring. These offspring become the F2 generation.
u Discovered the traits controlled by the recessive allele appeared again in the F2 generation.
u Dominant allele masked the recessive allele
u It reappeared because the recessive allele had separated (segregated) from the dominant allele.
u Segregation must have occurred during the formation of “gametes”