gregor mendel and genetics the work of mendel genetics = scientific study of heredity heredity =...
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Gregor Mendel and Genetics
The Work of Mendel• Genetics = scientific study of heredity• Heredity = characteristics that are
passed on to the next generation• Gregor Mendel (1800’s)
– Grew up as a peasant farmer– Austrian Monk, high school science
teacher, in charge of monastery gardens.– Used garden peas for experiments
Mendel was successful because: peas are self-pollinating (inherit all
characteristics from plant that bore them)
Had true breeding stock = basis for experiment
Can cross pollinate (uses 2 parents) Controlled experiment Kept careful records !
Traits studied
Chose several traits that were true-breeding and had two distinct forms
Seed shape: round vs wrinkled
Seed color: Yellow vs green Gray seed coat vs white seed coat Smooth pod shape vs constricted pod Pod color = green vs yellow Flower position = axial vs terminal Height = tall vs short
Mendel’s ExperimentP = parental generation, original pair, true
breeding, tall x shortCross pollination:F1 generation = first filial generation
results in hybrids (from parents with contrasting traits)
results: all tallSelf pollination:F2 generation = second filial generation
¾ tall, ¼ short
MENDEL’S CONCLUSION:
“Factors” governed the expression of each trait (factors now called ?)
Each trait = controlled by a pair of genes, two factors
(ex. 1 for tall, 1 for short)
Allele = different forms of a trait, one of the gene pair
Principle of Dominance
• 1 of the genes in a pair may prevent the other gene from being expressed.
• Dominant gene = one which masks the other in a pair
• Recessive gene = one which is hidden (may reappear in F2)
• Dominant allele = expressed by a capital letter (ex. Y = yellow)
• Recessive allele = lower case (ex. y = green)
Principle of Segregation
• Members of each pair of genes separate during gamete formation **********