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

2. Gregor Mendel
an Austrian monk who used garden pea plants to explain the inheritance of characteristics
Gregor Mendel ( )

3. Gregor Mendel Mendel examined seven different pea traits
each trait had only two possible variations (alleles)
Gregor Mendel ( )

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

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

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

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

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

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

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

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

16. 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

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

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

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

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

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

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

23. 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

24. 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

25. 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

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

27. 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

28. 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)

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

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

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

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

33. 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)

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

36. 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

37. 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

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