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Transcript of Gregor Mendel
Can also be cross pollinated by hand. Pea plants were great to use. They are a true breeding plant. They consistently produce offspring with only one form of a trait. Mendel would transfer the male gamete from one plant's flower to the female reproductive organ in the flower of another plant. (heredity) - the passing of traits to the next generation. Inheritance certain varieties of garden pea plants produced specific forms of a trait, generation after generation. Observations of Mendel's Work ie. some varieties always produced green seeds and others always produced yellow seeds. He cross pollinated a green seeded plant with a yellow seeded plant. These were the parent generation (P).
(he removed the male organs of the yellow seeded plant to prevent self pollination. Mendel's experiment P generation (pure breeding) F1 (first filial generation) F2 (second filial generation) Green seed trait seems to have disappeared 3:1 (yellow :green) entire year taken to test "true breeding"
peas produced flowers that would easily protect against foreign pollination
peas can be grown in large numbers and reproduction can be manipulated
peas have both male and female reproductive organs Seven Pea Plant Traits Flower color: purple or white
Flower position: axial or terminal
Stem length: long or short
Seed shape: round or wrinkled
Seed color: yellow or green
Pod shape: inflated or constricted
Pod color: yellow or green Why Peas? Mendel's Laws or Principles of Inheritance The Principle of Genes in Pairs Genetic characters are controlled by unit factors (genes) that exist in pairs in individual organisms and are passed from parents to their offspring. When two organisms produce offspring, each parent gives the offspring one of the factors from each pair. The Principle of Dominance and Recessiveness When two unlike factors responsible for a single character are present in a single individual, one factor can mask the expression of another factor; that is, one factor is dominant to the other, which is said to be recessive. The Principle of Segregation During the formation of gametes, the paired factors separate (segregate) randomly so that each gamete receives one factor or the other. The Principle of Independent Assortment During gamete formation, segregating pairs of factors assort independently of each other. Example: each pea plant has two genes that control pea texture. There are two possible textures (smooth and wrinkled) and therefore, two different genes for texture. Example: color genes do not trade off with genes for texture. Color genes only trade off with color genes from the opposing allelic sight.
The end result?? Each gamete produced by the parent is uniquely different as far as the traits that it codes for from every other gamete that is produced. Interesting Fact! For many creatures, this available statistical variation is so huge that in all probability, no two identical offspring will ever be produced even given trillions of years of time!! He experimented with only true breeding plants
He only measured absolute characteristics such as color, shape and texture of the offspring
His data was expressed numerically and subjected to statistical analysis
He looked through several successive generations of his pea plants and recorded their variations.
He was careful to pay close attention to procedure and detail Scientific Method Example: a pea plant's inheritance of the ability to produce purple flowers instead of white ones does not make it more likely that it would also inherit the ability to produce yellow peas in contrast to green ones. His method of reporting data and his large sampling size gave credibility to his research. Credibility!! 4 Important Conclusions The inheritance of each trait is determined by "units" or "factors" (genes) that are passed on to descendents unchanged. Gregor Mendel An individual inherits one such unit from each parent for each trait. A trait may not show up in an individual but can still be passed on to the next generation The genes for each trait segregate themselves during gamete production.