1. Mendelian Genetics Complete, Incomplete & Codominance

2. Gregor Mendel
Father of Genetics

3. Terms GENETICS: The study of heredity or inheritance of traits.
TRAIT: A specific characteristic that can be passed from parent to offspring
HEREDITY: the passing of traits/genes from one generation to the next

4. Mendelian Genetics Examines the physical characteristics
Principals and laws come from experiments by Mendel
Predicts inheritance patterns from generation to generation from generation to generation

5. Peas Self-pollinating Cheap Easy to grow High yield Edible
7+ traits that show complete dominance…
Peas

6. Parental or P Generation
(Original pair of plants)
Self-pollination (Pollen and egg are derived from the same plant)
Cross-Pollination (Pollen and egg are derived from different plants)
Purebred vs. Hybrid
Mendel Studied Seven Traits That Bred True

7. Monohybrid crosses P
Mendel crossed a tall plant with a short plant test.
The first group of offspring were called F1 generation for filial . They should have had blended traits, but didn’t…. F1

8. Proposals
Law of Dominance: when two different alleles for a single gene are present, one is dominant and one is recessive.
A pea plant contains two discrete hereditary factors, one from each parent
The two factors may be identical or different
When the two factors of a single trait are different
One is dominant and its effect can be seen
The other is recessive and is not expressed

9. Dominance some traits mask expression of others
Tall plant
Short plant
some traits mask expression of others
Dominant & Recessive allele traits
Dominant  -  trait that does not disappear in the F1
Recessive -  trait that disappears in the F1 generation   
each individual possess [only] 2 alleles for a specific trait          
    RR  -   homozygous dominant
Rr   -   heterozygous rr   -   homozygous recessive T T t t T t F1
All tall plants T t

10. The Law of Segregation
Each pair of genes segregate or separate during Meiosis and the sex cells carry only one copy of each gene
We know that now because we know about meiosis, but Mendel “discovered” this through analyzing his results…
Tt ´ Tt cross
Tall plant
Tall plant F1 T t T t F2
Tall
Tall
Tall
Short T T T t T t t t

11. The data suggested a theory of inheritance
Results for all seven traits studied:
The F1 generation showed only one of the two parental traits
The F2 generation showed an ~ 3:1 ratio of the two parental traits
These results contradicted a blending mechanism of heredity
During gamete formation, the paired factors segregate randomly so that half of the gametes received one factor and half of the gametes received the other
This is Mendel’s Law of Segregation

12. Conclusions Gene: a section of chromosome that codes for a trait
Most organisms have 2 copies of every gene
one from each parent
Alleles: various forms of a trait or gene
During gamete formation, the paired factors segregate randomly so that half of the gametes received one factor and half of the gametes received the other
This is Mendel’s Law of Segregation

13. Probability
Probability is used to show all possible combinations of gametes and the likelihood that each will occur
Like flipping a coin
In reality, you don’t get the exact ratio of results
Rules are up to chance
PUNNETT SQUARES CAN BE USED TO DETERMINE THE PROBABILITY OF AN ALLELE OCCURING IN THE OFFSPRING

14. Punnett Squares T T t Tt Tt t Tt Tt
a grid that enables one to predict the outcome of simple genetic crosses
by the English geneticist, Reginald Punnett T T t Tt Tt t Tt Tt

15. R r RR Rr R Rr rr r

16. HOMOZYGOUS
organisms have 2 identical alleles for a particular trait and are called true-breeding
Homo = samo
HH or hh
AA or aa
GG or gg
QQ or qq

17. HETEROZYGOUS
organisms have 2 different alleles for the same trait and are called hybrids
He-te-ro = dif-fer-ent Hh Aa Gg Qq

19. Homologous Chromosome 4a A
Axial
Terminal
Inflated D d
Constricted T t
Tall
Short

20. Results of Monohybrid Cross
PHENOTYPE 
(PHYsical
appearance)  
3 round    to   1 wrinkled          
GENOTYPE    
(allele make up)     
1(RR)  to 
2(Rr)  to  1(rr)  

21. Dihybrid Crosses Mendel also performed a For example
Crossing individual plants that differ in two traits
For example
Trait 1 =  Seed texture (round vs. wrinkled)
Trait 2 = Seed color (yellow vs. green)

23. Update… Mendelian factors are now called genes
Alleles are different versions of the same gene
An individual with two identical alleles is termed homozygous
An individual with two different alleles, is termed heterozygous
Phenotype refers to the outward appearance of an individual
Genotype refers to the specific allelic composition of an individual

26. Meiosis backs Mendel
The segregation of chromosomes in anaphase I of meiosis explains Mendel’s observation that each parent gives one allele for each trait at random to each offspring, regardless of whether the allele is expressed.
The segregation of chromosomes at random during anaphase I also explains how factors, or genes, for different traits are inherited independently of each other.

27. Incomplete, Codominance, Multiple Alleles, and Sex-linked Traits
Beyond Mendel
Incomplete, Codominance, Multiple Alleles, and Sex-linked Traits

28. Incomplete Dominance Blended Inheritance neither gene is dominant
i.e., both contribute to expression of the trait
there is an intermediate phenotype…
Similar to mixing paint

29. R’ R’ R
RR’
RR’ R
RR’
RR’

30. R’ R R
RR’ RR R’
RR’
R’R’

31. Red x White = Pink

32. Codominance Co—together, at the same time Equal expression
Neither recessive
Moo!
Methane

34. Morgan’s Experiment
The chromosome theory of inheritance was confirmed through studies carried out by Thomas Hunt Morgan
Morgan tried to induce mutations in the fruit fly Drosophila melanogaster
Treatments included
Rearing in the dark
X-rays
Radium
After 2 years, Morgan finally obtained an interesting result
A male fruit fly with white eyes rather than the normal red eyes
Morgan reasoned that this white eyed male must have arisen from a new mutation that converted a red-eyed allele into a white-eyed allele
Morgan followed Mendel’s approach in studying the inheritance of this white-eyed trait
He made crosses then analyzed their outcome quantitatively

35. Colorblindness...

36. Frequency of crossover exchange
Frequency of crossover exchange...           exchange of chromatids pieces of a homologous pair during synapsis at a chiasma...      is GREATER the FARTHER apart 2 genes are    is proportional to relative distance                                       between 2 linked genes    Relative distance is measured as...        1% crossover frequency =                                   1 map unit of map distance               above CO Freq  =   8.5% + 8.5% = 17%        1%   CrossOver  Freq   =    1   centiMorgan

37. Polygenic (Quantitative Trait) Inheritance
Two or more genes affect 1 phenotype  usually with quantitative characters,  with a continuous scale of measurement  - height,  weight,  color* (and a  polygenic*model), etc...

39. Environmental Influences on Genes