1. Gregor Johann Mendel Austrian monk, mathematician by trade
Mendelian Genetics
12/4/2018
Gregor Johann Mendel
Austrian monk, mathematician by trade
Studied the inheritance of traits in pea plants
Developed the laws of inheritance
Mendel's work was not recognized until the turn of the 20th century
Between 1856 and 1863, Mendel cultivated and tested some 28,000 pea plants
He found that the plants' offspring retained traits of the parents
Called the “Father of Genetics"

2. Mendelian Genetics
12/4/2018
Site of Mendel’s experimental garden in the Czech Republic Note the ratio of flower colors…
Fig. 5.co

3. Mendelian Genetics
12/4/2018
Genetic Terminology
Trait - any characteristic that can be passed from parent to offspring
Heredity - passing of traits from parent to offspring
Genetics - study of heredity

4. Mendel’s Pea Plant Experiments
Mendelian Genetics
12/4/2018
Mendel’s Pea Plant Experiments

5. Mendel’s Experimental Methods
Mendelian Genetics
12/4/2018
Mendel’s Experimental Methods
Mendel hand-pollinated flowers using a paintbrush
He snipped the stamens to prevent self-pollination
Covered each flower with a cloth bag
He traced 8 traits through the several generations
Ultimately he produced pure strains for each

6. Mendelian Genetics
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7. Mendelian Genetics
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8. Mendel’s Flowers
Once the pure strains were made; Mendel then began systematically crossing plants, this time however, he let the plants self-pollinate. Why?
He observed the offspring produced for each trait, in each generation, for any patterns that appeared.
Mendel’s questions:
If traits are known, can the inheritance of the traits in offspring be predicted?
What is the ‘mechanism’ for inheritance?

9. Mendelian Genetics
12/4/2018
Generation “Gap”
Parental P1 Generation = the parental generation in a breeding experiment, the pure strain
F1 generation = the first-generation offspring in a breeding experiment. (1st filial generation)
F2 generation = the second-generation offspring in a breeding experiment. (2nd filial generation)

10. White trait reappeared
WHY no white?
What happened to the
white trait?
White trait reappeared
in this generation,
so there must be some
‘factor’ in the purple
flower that masked it

11. Mendelian Genetics
12/4/2018
Mendel’s Conclusions
Dominant – trait that was expressed if present; represented by a capital letter (R)
Recessive – trait that is expresses only if the dominant is not present; represented by a lowercase letter (r)
Factors: sequence of DNA that codes for a trait, today we know those are the GENES
Alleles - two forms of a gene (dominant & recessive)
Ex: Trait(Gene)=Flower Color
Alleles=Purple/White
Regardless of the trait, results were the same and could be predicted in future generations…Mendel developed his first law of genetics; the Law of Dominance
Maternal
Chromosome
Paternal
Chromosome

12. Mendelian Genetics
12/4/2018
Law of Dominance
In a cross of parents(P) that are pure for contrasting traits, only one form of the trait will appear in the next generation(F1).
All the offspring will be heterozygous and express only the dominant trait.
RR x rr yields all Rr

13. Mendelian Genetics
12/4/2018
Mendelian Genetics

14. Eight Pea Plant Traits GENE ALLELES GENE ALLELES Mendelian Genetics
12/4/2018
Eight Pea Plant Traits
GENE
ALLELES
GENE
ALLELES

15. Let’s see how it works, by adding the allele notations…RR rr Rr
Rr x Rr Rr rr RR Rr

16. Predictable Generations
Mendelian Genetics
12/4/2018
Predictable Generations
Cross 2 Pure Plants TT x tt
Results in all Hybrids Tt
Cross 2 Hybrids get 3 Tall & 1 Short TT,Tt,Tt,tt

17. You try one…Let’s use Seed Color
P generation YY yy Yy Yy Yy Yy F1
All Yy, yellow YY Yy Yy yy
¾ yellow
¼ YY, 2/4 Yy
¼ green
¼ yy F2 YY Yy Yy yy

18. GENOTYPEs Genotype - allele combination for a trait
Mendelian Genetics
12/4/2018
GENOTYPEs
Genotype - allele combination for a trait
Homozygous – allele combination involving two of the same alleles; can be either
Homozygous dominant: RR
Homozygous recessive: rr
Heterozygous – allele combination of one dominant & one recessive allele 
Heterozygous: Rr

19. PHENOTYPE
Phenotype - the physical features resulting from the genotype; am I…
Phenotype also refers to your chemical features as well; enzymes and functional proteins are also determined by genes and allele combinations
PURPLE
or, am I
WHITE

20. Genotype & Phenotype in Seed Color
Mendelian Genetics
12/4/2018
Genotype & Phenotype in Seed Color
Genotype of alleles: R = yellow seed r = green seed
In the F2
The possible combinations are:
SPIDERMAN
Genotypes RR Rr rr
Phenotypes YELLOW YELLOW GREEN

21. Mendelian Genetics
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Punnett Squares
Diagram that is used to predict an outcome of a particular cross or breeding experiment
Illustrate Mendel’s second law
Law of Segregation

22. Mendelian Genetics
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23. Mendelian Genetics CROSSES INVOLVING 1 GENE: 2 ALLELES
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Monohybrid crosses
CROSSES INVOLVING 1 GENE: 2 ALLELES

24. P1 Monohybrid Cross r r Rr Rr R R Rr Rr Trait: Seed Shape
Mendelian Genetics
12/4/2018
P1 Monohybrid Cross
Trait: Seed Shape
Alleles: R – Round r – Wrinkled
Cross: Round seeds x Wrinkled seeds
RR x rr r r
Genotype: Rr Ratio: 1:1 or 100%
Phenotype: Round Ratio: 1:1 or 100% Rr Rr R R Rr Rr

25. F1 Monohybrid Cross R r RR Rr R r Rr rr Trait: Seed Shape
Mendelian Genetics
12/4/2018
F1 Monohybrid Cross
Trait: Seed Shape
Alleles: R – Round r – Wrinkled
Cross: Round seeds x Round seeds
Rr x Rr
Genotype: RR, Rr, rr
Ratio: 1:2:1
Phenotypes:
Round & wrinkled
Ratio: 3:1 R r RR Rr R r Rr rr

26. P1 Monohybrid Cross Review
Mendelian Genetics
12/4/2018
P1 Monohybrid Cross Review
Homozygous dominant x Homozygous recessive
Offspring all Heterozygous (hybrids)
Offspring called F1 generation
Genotypic & Phenotypic ratio is ALL ALIKE

27. F1 Monohybrid Cross Review
Mendelian Genetics
12/4/2018
F1 Monohybrid Cross Review
Heterozygous x heterozygous
Offspring: 25% Homozygous dominant RR 50% Heterozygous Rr 25% Homozygous Recessive rr
Offspring called F2 generation
Genotypic ratio is 1:2:1
Phenotypic Ratio is 3:1

28. Results of Monohybrid Crosses
Mendelian Genetics
12/4/2018
Results of Monohybrid Crosses
Inheritable factors or genes are responsible for all heritable characteristics
Phenotype is based on Genotype
Each trait is based on two genes, one from the mother and the other from the father
True-breeding individuals are homozygous ( both alleles) are the same

29. Law of Independent Assortment
Mendelian Genetics
12/4/2018
Law of Independent Assortment
Alleles for different traits are distributed to sex cells (& offspring) independently of one another.
This law can be illustrated using dihybrid crosses.

30. Mendelian Genetics
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Dihybrid Cross
A breeding experiment that tracks the inheritance of two traits.
Mendel’s “Law of Independent Assortment”
a. Each pair of alleles segregates independently during gamete formation
b. Formula: 2n (n = # of heterozygotes)

31. Answer: 1. RrYy: 2n = 22 = 4 gametes RY Ry rY ry
Mendelian Genetics
12/4/2018
Answer:
1. RrYy: 2n = 22 = 4 gametes
RY Ry rY ry
2. AaBbCCDd: 2n = 23 = 8 gametes
ABCD ABCd AbCD AbCd
aBCD aBCd abCD abCD
3. MmNnOoPPQQRrssTtQq: 2n = 26 = 64 gametes

32. All possible allele combinations
Mendelian Genetics
12/4/2018
Dihybrid Cross
Traits: Seed shape & Seed color
Alleles: R round Y yellow r wrinkled y green
To help determine allele combinations use the math order of operations FOIL
First-Outside-Inside-Last
RrYy x RrYy
RY Ry rY ry
RY Ry rY ry
All possible allele combinations

33. Dihybrid Cross RY Ry rY ry RY Ry rY ry Rryy RRYy RrYY RrYy
Mendelian Genetics
12/4/2018
Dihybrid Cross RY Ry rY ry RY Ry rY ry
Rryy RRYy RrYY RrYy
RRYy Rryy RrYy Rryy
RrYY RrYy rrYY rrYy
RrYy Rryy rrYy rryy

34. Dihybrid Cross Round/Yellow: 9 Round/green: 3 wrinkled/Yellow: 3
Mendelian Genetics
12/4/2018
Dihybrid Cross
Round/Yellow: 9
RRYY 1
RRYy 2
RrYY 2
RrYy 4
Round/green: 3
RRyy 1
Rryy 2
wrinkled/Yellow: 3
rrYY 1
rrYy 2
wrinkled/green: 1
Rryy 1
9:3:3:1 phenotypic ratio RY Ry rY ry
RRYY
RRYy
RrYY
RrYy
RRyy
Rryy
rrYY
rrYy
rryy

35. Mendelian Genetics
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Dihybrid Cross
Round/Yellow: 9 Round/green: 3 wrinkled/Yellow: 3 wrinkled/green: 1
9:3:3:1

36. Mendelian Genetics
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copyright cmassengale
Question: How many gametes will be produced for the following allele arrangements?
Remember: 2n (n = # of heterozygotes)
1. RrYy
2. AaBbCCDd
3. MmNnOoPPQQRrssTtQq

37. Genetic Practice Problems
Mendelian Genetics
12/4/2018
copyright cmassengale
Genetic Practice Problems

38. Breed the P1 generation tall (TT) x dwarf (tt) pea plants t T
Mendelian Genetics
12/4/2018
copyright cmassengale
Breed the P1 generation
tall (TT) x dwarf (tt) pea plants t T

39. tall (TT) vs. dwarf (tt) pea plants
Mendelian Genetics
12/4/2018
copyright cmassengale
Solution:
tall (TT) vs. dwarf (tt) pea plants T t
All Tt = tall
(heterozygous tall)
produces the
F1 generation Tt

40. Breed the F1 generation tall (Tt) vs. tall (Tt) pea plants T t T t
Mendelian Genetics
12/4/2018
copyright cmassengale
Breed the F1 generation
tall (Tt) vs. tall (Tt) pea plants T t T t

41. tall (Tt) x tall (Tt) pea plants
Mendelian Genetics
12/4/2018
copyright cmassengale
Solution:
tall (Tt) x tall (Tt) pea plants T t
produces the
F2 generation
1/4 (25%) = TT
1/2 (50%) = Tt
1/4 (25%) = tt
1:2:1 genotype
3:1 phenotype TT Tt tt