1. Gregor Johann Mendel “Father of Genetics”
Mendelian Genetics
12/7/2018
Gregor Johann Mendel
“Father of Genetics”
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

2. Mendelian Genetics
12/7/2018
Genetic Terminology
Trait - any characteristic that can be passed from parent to offspring by genes(code on DNA) and their alleles(specific protein sequences)
Heredity - passing of traits from parent to offspring
Genetics - study of heredity

3. Mendel’s Experimental Methods
Mendelian Genetics
12/7/2018
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 7 traits through the several generations
Ultimately he produced pure strains for each

4. Seven Pea Plant Traits GENE ALLELES GENE ALLELES Mendelian Genetics
12/7/2018
Seven Pea Plant Traits
GENE
ALLELES
GENE
ALLELES

5. Mendel’s Flowers Mendel’s questions:
If traits are known, can the inheritance of the traits in offspring be predicted?
What is the ‘mechanism’ for inheritance?
With his pure strains Mendel began systematically crossing plants, observing one trait at a time:
Monohybrid Crosses = 1 gene and its 2 alleles
He let the plants self-pollinate during these experiments
He observed the offspring produced for each trait, in each generation, for any patterns that appeared.

6. First filial generation of offspring
PURE STRAINS
WHY no white?
What happened to the
white trait?
First filial generation
of offspring
Second filial generation
White trait reappeared
in this generation,
so there must be some
‘factor’ in the purple
flower that masked it

7. Mendelian Genetics
12/7/2018
Mendel’s Flowers

8. Mendelian Genetics
12/7/2018
Mendel’s Conclusions
The trait that is expressed if present he called dominant; 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 –variant(protein code) of a gene (dominant and/or 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
Gene Flower Color
Maternal
Chromosome
Paternal
Chromosome

9. 100% of the F1 offspring will express only the “dominant” trait.
Mendelian Genetics
12/7/2018
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 F1
100% of the F1 offspring will express only the “dominant” trait.

10. Let’s see how the Law of Dominance works, by adding the allele notations…RR rr Rr
Rr x Rr Rr rr RR Rr

11. Let’s Practice! Using a yellow and a green colored pencil fill in the circles representing pea seed color. Then fill in the allele notations. YELLOW(R) is dominant GREEN(r) is recessive   RR rr rr Rr Rr RR Rr Rr rr

12. GENOTYPEs Possible allele combinations for a trait
Mendelian Genetics
12/7/2018
GENOTYPEs
Possible allele combinations 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

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

14. MONOHYBRID CROSSES
PUNNETT SQUARES

15. Mendelian Genetics
12/7/2018
Punnett Squares
Diagram that is used to predict an outcome of a particular cross or breeding experiment
Illustrate Mendel’s Second Law of Genetics:
Law of Segregation

16. RR rr Rr RR Rr rr RR Rr Rr rr 1 2 3 4 5 6 Homozygous Dominant Parents
Recessive Parents 2
HDP X HRP P1 3 R R r r R R RR rr Rr R r r R r r
G: 4: Ph: 4:4
G: 4: Ph: 4:4
G: 4: Ph: 4:4
Heterozygous
Parents F2 4 5
HDP X Hetero 6
HRP X Hetero R r R R r r RR Rr rr RR Rr Rr rr R R R r r r
G: 1:2:1 Ph: 3:1
G: 2: Ph: 4:4
G: 2: Ph: 2:4

17. EYES ee Ee 50 E e e Ee ee e Ee ee BLUE Ee KERMIT EYES BLACK ee NOSE
1. TOSS A COIN TO DETERMINE
DOMINANT ALLELE FOR EACH
TRAIT.
2. THE OPPOSITE TRAIT IS THE
RECESSIVE
3. TOSS THE COIN AGAIN TO
DETERMINE THE SECOND
ALLELE FOR ANY DOMINANT
GENOTYPE
4. COMPLETE THE PUNNETS FOR
EACH TRAIT USING YOUR
PARENT CHARACTER’S
GENOTYPES. THESE BECOME
THE TRAITS THEIR CHILD
INHERITS.
KERMIT
EYES
BLACK ee
NOSE
NONE
SKIN
GREEN
MISS PIGGY
EYES
BLUE E e
NOSE
SNOUT
SKIN
PINK
EYES
ee Ee 50
E e
e Ee ee
e Ee ee
5. SINCE THIS SQUARE
SHOWS A 50/50 CHANCE
A COIN MUST BE TOSSED TO
DETERMINE WHICH THE OFFSPRING
WILL INHERIT
BLUE Ee

18. EYES E BLUE BLACK e Ee ee Ee
6. TRANSFER YOUR DATA FROM THE WORKSHEET TO THIS CHART
EYES E BLUE BLACK e Ee ee Ee
7. Though not required, you can select more than 5 traits. If so, complete those
punnetts on a separate page then add rows to this chart

20. 8. TOSS A COIN TO DETERMINE
SEX OF THE OFFSPRING
9. DRAW YOUR OFFSPRING
BASED UPON THE INHERITED
TRAITS
10. TAPE, DON’T STAPLE, YOUR
OFFSPRING TO THE DIAGRAM
DUE ON OR BEFORE MONDAY 1/29

24. RR rr Rr RR Rr rr RR Rr Rr rr 1 2 3 4 5 6 Homozygous Dominant Parents
Recessive Parents 2
HDP X HRP P1 3 R R r r R R RR rr Rr R r r R r r
G: 4: Ph: 4:4
G: 4: Ph: 4:4
G: 4: Ph: 4:4
Heterozygous
Parents F2 4 5
HDP X Hetero 6
HRP X Hetero R r R R r r RR Rr rr RR Rr Rr rr R R R r r r
G: 1:2:1 Ph: 3:1
G: 2: Ph: 4:4
G: 2: Ph: 2:4