Lesson Outline Gregor Mendel Genetic Laws and Principles Crosses Generation Terms Punnett Squares

Gregor Mendel an Austrian monk who used garden pea plants to explain the inheritance of characteristics Gregor Mendel (1822-1884)

Gregor Mendel Mendel examined seven different pea traits each trait had only two possible variations (alleles) Gregor Mendel (1822-1884)

Gregor Mendel Mendel was the first individual to propose the principal of dominance, the law of segregation, and the law of independent assortment

Lesson Outline √ Gregor Mendel Genetic Laws and Principles Crosses Generation Terms Punnett Squares

Genetic Laws and Principles Principle of Dominance when individuals with different alleles reproduce, the offspring will only express the dominant trait

Genetic Laws and Principles Law of Segregation chromosome pairs split up during meiosis with one member of each pair going into separate gametes

Genetic Laws and Principles Law of Independent Assortment the inheritance of traits are independent of each another

Lesson Outline √ √ Gregor Mendel Genetic Laws and Principles Crosses Generation Terms Punnett Squares √

Crosses we will be looking at three different types of crosses… Monohybrid Cross involves one trait a

Crosses we will be looking at three different types of crosses… Dihybrid Cross involves two traits

Crosses we will be looking at three different types of crosses… Test Cross involves the cross of an individual with a homozygous recessive individual (bb) in order to determine the phenotype of the first individual

Lesson Outline √ √ √ Gregor Mendel Genetic Laws and Principles Crosses Generation Terms Punnett Squares √ √

Generation Terms P1 = parent generation F1 = first filial generation (children) F2 = second filial generation (grandchildren)

Lesson Outline √ √ √ √ Gregor Mendel Genetic Laws and Principles Crosses Generation Terms Punnett Squares √ √ √

Punnett Squares a punnett square is a chart used by geneticists to determine the probability of results when two individuals are crossed

Punnett Squares in monohybrid crosses, a 2 x 2 punnett square is used

Punnett Squares the possible gametes produced by the parents are written at the top and along the side B b Mother = Bb

Punnett Squares the possible gametes produced by the parents are written at the top and along the side B b b Mother = Bb Father = bb b

Punnett Squares the gametes are combined to produce all of the possible F1 genotypes B b b Bb bb Mother = Bb Father = bb b Bb bb

Find the genotypes and phenotypes of the F1 and F2 generations when a homozygous tall (T) pea plant is crossed with a homozygous short (t) plant Given: Parent A = TT Parent B = tt t t Gametes: T T

T T t Tt Tt Tt Tt t F1 genotypes = all Tt F1 phenotypes = all tall

to find the F2 generation, you cross the offspring produced in the F1 generation Given: Parent A = Tt Parent B = Tt Gametes: T t T t

T t T TT Tt Tt tt t F2 genotypes = 1 TT : 2 Tt : 1 tt (1:2:1 ratio) F2 phenotypes = 3 tall : 1 short (3:1 ratio)

Punnett Squares in the case of a cross that involves parents that are homozygous for a particular trait:

Punnett Squares F1 will always have: Genotypes that are heterozygous Phenotypes that resemble the dominant trait

T T t Tt Tt Tt Tt t F1 genotypes = all Tt F1 phenotypes = all tall

Punnett Squares F2 will always have a: Genotypic ratio of 1:2:1 1 homozygous dominant 2 heterozygous 1 homozygous recessive Phenotypic ratio of 3:1 3 dominant 1 recessive

T t T TT Tt Tt tt t F2 genotypes = 1 TT : 2 Tt : 1 tt (1:2:1 ratio) F2 phenotypes = 3 tall : 1 short (3:1 ratio)

(homozygous recessive) Test Cross unknown parent BB? or Bb? known parent bb (homozygous recessive) x

Test Cross Case #1 – unknown parent = BB if all F1 show the dominant trait, then the unknown parent was BB b Bb Bb Bb Bb b

Test Cross Case #2 – unknown parent = Bb if even one F1 shows the recessive trait, then the unknown parent was Bb b Bb bb Bb bb b

Lesson Outline √ √ √ √ √ Gregor Mendel Genetic Laws and Principles Crosses Generation Terms Punnett Squares √ √ √ √