Mendel’s Laws

Essential Questions 1. Who is Gregor Mendel? 2. What happened in Mendel’s monohybrid cross experiment? 3. What happened in Mendel’s dihybrid cross experiment? 4. What did Mendel learn from his first experiment? (Hint: There are fourrules/laws)

Mendel’s Laws Rule of Unit Factors Rule of Dominance Law of Segregation Law of Independent Assortment

Who is Mendel? -Gregor Mendel: Austrian monk, the father of modern genetics Genetics: the branch of biology that studies heredity

Who is Mendel? -Gregor Mendel: Austrian monk, the father of modern genetics Genetics: the branch of biology that studies heredity -Heredity: the passing on of characteristics from parents to offspring -Trait: any inherited characteristic Mendel studied pea plants

-Pea plants reproduce sexually -Gametes: male or female sex cells -Fertilization: when the male and female gametes unite -Zygote: a fertilized cell -Pollination: the transfer of pollen grains from a male reproductive organ to a female reproductive organ -Hybrid: the offspring of parents that have different forms of a trait

Mendel did two types of crosses: 1.Monohybrid cross: when Mendel crossed two plants that differed in only one trait (height) 2. Dihybrid cross: a cross between organisms that differ in two traits rather than only one (pea color and pea texture)

Mendel’s monohybrid cross: Short x Tall

Mendel’s Monohybrid Cross First generation cross: (short x tall) Result: All offspring were tall. Second generation cross: (tall offspring x tall offspring): Result: Mendel found that 75% of the third generation offspring were tall; 25% were short.

Mendel’s Dihybrid Cross -Two traits: Pea color (green or yellow) Pea texture (smooth or wrinkled) -P generation: Yellow, wrinkled x green, smooth -F1 generation: All yellow, smooth -If you cross F1 x F1 9 round yellow 3 round green 3 wrinkled yellow 1 wrinkled green

The unexpected outcomes from Mendel’s crosses allowed him to observe the following laws: 1. The rule of unit factors: Each organism has two forms of each gene. Allele: one of two different gene forms

From his experiments, Mendel formulated the following laws: 1. The rule of unit factors: Each organism has two alleles for each gene. Allele: one of two different gene forms 2. The rule of dominance: When both allele forms are found in a trait, the dominant allele is expressed over the recessive allele Dominant: the expressed trait Recessive: the trait that is unseen 3. The law of segregation: when gametes are produced, each gamete receives one of two possible alleles

From his experiments, Mendel formulated the following laws: 1. The rule of unit factors: 2. The rule of dominance: 3. The law of segregation: when gametes are produced, each gamete receives one of two possible alleles -For each gene, fertilization unites one allele from the mother with one allele from the father 4. The law of independent assortment Genes from different traits are inherited independently of each other

Essential Questions 1. Who is Gregor Mendel? 2. What happened in Mendel’s monohybrid cross experiment? 3. What happened in Mendel’s dihybrid cross experiment? 4. What did Mendel learn from his first experiment? (Hint: There are fourrules/laws)

Essential Questions 1. Who is Gregor Mendel? Father of Modern Genetics; studied heredity 2. What happened in Mendel’s monohybrid cross experiment? He crossed a tall pea plant with a short pea plant, to get 100% tall in the first generation and 75% tall in the second generation 3. Dihybrid cross experiment: Mendel observed a 9:3:3:1 ratio of traits 3. What did Mendel learn from his first experiment? (Hint: There are three rules/laws) Rule of unit factors, Rule of dominance, Law of segregation, Law of Independent Assortment