1. Unit 7
Genetics

2. Mendelian Genetics

3. Heredity Terminology
Self-fertilization – sexually reproducing organism reproducing with itself
Common in hermaphroditic flowering plants
Or, plant breeders (gardeners) will do this to the plant
True-breeding (purebred) – refers a population that always produces the same trait(s)
Results from many self-fertilized generations
Populations are genetically very similar

4. X Heredity Terminology
Cross-fertilization – reproduction between two different organisms
Usually refers to two different true-breeding plants
Example: true-breeding purple flower peas mated with true- breeding white purple flower peas
Hybrid – offspring of purebreds X

5. Heredity Terminology Generations P generation – true- breeding
F1 generation – P generation offspring
F2 generation – offspring when F1 generation self- fertilizes (or fertilize each other)

6. Homologous chromosomes and Alleles
Homologous chromosomes, genes, alleles
Allele – different variations of the same genes
Example: Gene: flower color
Alleles: purple gene or white gene

7. Gregor Mendel Austrian monk Lived during the 1800s
“Father of Genetics”
Use garden pea plants to do his research
Recorded accurate data (kinda)
Observed large populations
Why pea plants?

8. 7 Traits studied by Mendel
Obj 3
7 Traits studied by Mendel
Seed shape (round vs wrinkled)
Seed color (yellow vs green)
Seed coat color (brown vs white)
Pod color (green vs yellow)
Pod shape (inflated vs wrinkled)
Stem Length (long vs short)
Flower Position (axial vs terminal)

9. Major Observations by Mendel
Traits are not simply blended
Many pea plant traits came in pairs
When starting with true- breeding P generation plants traits will skip the F1 generation and reappear in the F2 generation.
Occurs across all 7 traits and in the same ratio!!!!!

11. Mendel’s four hypotheses
There are different versions of genes (alleles)
Mendel’s 7 pea plant traits only have 2 alleles.
But, there can be more than 2 alleles for genes (less than simple heredity)
Each organism inherits 2 alleles for each character. One from each genetic donor
Homozygous – 2 identical alleles (called a homozygote)
Heterozygous – 2 different alleles (called a heterozygote)

12. 3. Law of Dominance
Explains why all the F1 generation plants only show one trait.
Explains why the second trait reappears in the F2 generation.
When both alleles are inherited (heterozygous) the dominant allele controls the physical characteristic that is “seen”.
Recessive allele has no physical effect
Example: Gene – Seed coat
Dominant Allele – Round (R)
Recessive Allele – wrinkled (r) RR rr Rr

13. 4. Law of Segregation
2 alleles for a given trait separate during formation of the gametes (meiosis)
Each somatic cell (diploid) has 2 copies of each gene…
Each sex cell (haploid) has only one copy
Each parent passes on at RANDOM only 1 allele for each trait
Genes on separate chromosomes will sort independently

14. Punnett Square
Diagram used to determine the possible combination of alleles.
Use to predict the genotypic and phenotypic ratio of a cross.
Example: Shows the expected out come of cross between two heterozygous purple flowers P p
Gametes

15. Genotype and Phenotype Ratios
OBJ 5
Genotype and Phenotype Ratios
Genotype = Alleles
Phenotype = physical outcome of the combination of alleles
Genotypic ratio 1:2:1
Phenotypic ratio 3:1

16. Independent Assortment – Dihybrid Cross
Parents = RRYY x rryy
Gametes = RY x ry
F1 generation = RrYy
If the genes were independent, the F1 could make:
RY and ry gametes
Ry and rY gametes
Then we could do a dihybrid cross (or 2-factor cross) to find out possible offspring Y Y y y y y Y Y OR R R r r R R r r

17. 4 possible Female GametesRY Ry rY ry
RRYY
RRYy
RrYY
RrYy
RRyy
Rryy
rrYY
rrYy
rryy
4 possible Male Gametes
Dihybrid Cross
4 possible Female Gametes
Possible Zygotes

18. RY Ry rY ry RRYY RRYy RrYY RrYy RRyy Rryy rrYY rrYy rryy
Dihybrid Cross:
Genotypic ratio:
1:1:2:2:4:2:2:1:1 RY Ry rY ry
RRYY
RRYy
RrYY
RrYy
RRyy
Rryy
rrYY
rrYy
rryy
9 Different Genotypes

19. RY Ry rY ry RRYY RRYy RrYY RrYy RRyy Rryy rrYY rrYy rryy
Dihybrid Cross:
Phenotypic ratio:
9:3:3:1 RY Ry rY ry
RRYY
RRYy
RrYY
RrYy
RRyy
Rryy
rrYY
rrYy
rryy
4 Different Phenotypes

20. Rules of Probability
Rule of multiplication – two (or more) events both happen
Rule of addition – either of two events occur (or when an event can happen in 2 or more ways)
Examples:
When rolling a die twice, what is the chance of rolling a 4 both times?
You roll a die, what is probability of getting a 2 or a 4?

21. Rules of Probability – Genetics Applications
OBJ 10
Rules of Probability – Genetics Applications
What are the odds of two Cc parents have a child that is also Cc? (don’t use a Punnett square…try this with probability)
For two people with the genotypes AaBbCcDd, what are the odds they will have a child with all dominant alleles?

22. Alternative Inheritance
Non-Mendelian Patterns

23. Incomplete Dominance
Heterozygous individuals have an appearance that is intermediate between the phenotypes of a homozygous dominant organism and a homozygous recessive organism

24. 3 phenotypes and 3 genotypes
OBJ 11a
Homozygous Red
Heterozygous Pink
Homozygous White
3 phenotypes and 3 genotypes

25. Incomplete Dominance in Humans
LDL – Low density lipoproteins
LDL receptors remove LDLs from the blood stream.
Low expression of LDL receptors is one variable in the development of artherosclerosis

26. Codominance
Both alleles contribute to the phenotype of a heterozygous individual
Similar to incomplete dominance, but there is no mixing, both alleles are separately expressed in the phenotype

27. Multiple Alleles
Traits that are determined by more than 2 alleles
Example: fur coloring in rabbits
4 primary alleles
Agouti (C) > chinchilla (silver) (cch) > Himalayan (ch) > albino (ca)
>
Homozygous for each allele pictured

28. Human Blood Types – An example of Multiple Alleles, Codominance and Dominance
Multilpe Alleles – 3 alleles that express cell surface proteins
A – A protein
B – B protein
O – no protein
Codominance
AB blood – both proteins are expressed
Dominance
A over O
B over O

29. Matching Blood types – Why?
Red Blood Cell surface proteins interact with anti-bodies in the blood serum
Example – Antibody-B will bind to surface protein B and trigger the cells to clot, thus limiting/stopping blood flow.

30. Polygenic inheritance
Two or more genes contribute to a physical characteristic.
Example: Human Skin color (polygenic and incomplete dominance)

31. Sex-linked genes
Genes located on X chromosomes.
XX female
XY male

32. Hemophilia – Royal Families of Europe