1. Genetics

2. Gregor Mendel liked peas
Gregor Mendel was an Austrian monk who is known for studying inheritance in pea plants.
‘Father of Genetics’
Mendel as a toddler

3. Mendel’s Experiment Mate (cross) two different pea plants P x P
Results = F1 generation
F1 was hybrid
F1 x F1
F2 generation

4. What Mendel Found

5. What Mendel Found F2 generation had ¾ purple and ¼ white flowers
F1 generation had only purple flowers
White trait “disappeared”
F2 generation had ¾ purple and ¼ white flowers
Mendel observed 6 other traits of the pea plants and got similar results
In each case, one of the parental traits he was observing did not occur in the F1 generation but was found in ¼ of the F2 generation

6. Mendel’s Hypotheses There are alternate forms of genes called alleles
ie. Pea plants have a purple allele and a white allele
An Organism has 2 alleles for each gene. They get one from each parent.
2 of the same alleles = homozygous
2 different alleles = heterozygous

7. More of Mendel’s Hypotheses
In a heterozygous organism (has 2 different alleles), one allele might have a greater effect on the organism.
The allele that appears to effect the organism is the dominant allele.
The allele that appears to have no effect is the recessive allele.
In meiosis, the alleles separate when the chromatids separate. This is the principle of segregation.

8. Parents send information about traits to their offspring.
This information is what we refer to as genes.
Genes are located on chromosomes.

9. Each individual has two genes for each trait (one from each parent).
The two genes may or may not have the same information for each trait.
For example both of your parents gave you a gene for tongue rolling. Your mom might have given you the gene that says you can roll your tongue. While your dad might have given you the gene that says you cannot roll your tongue.

10. Phenotype of an organism is its physical appearance (what it is going to look like)
The genotype of an organism is the genes or letters that organism has for a trait.

11. If the dad cannot roll his tongue his genotype is tt
The ability to roll your tongue is a dominant trait, so it would be represented with a T
Not being able to roll your tongue would be a recessive trait represented with a t
If the dad cannot roll his tongue his genotype is tt
If the mom can roll her tongue her genotype is either TT or Tt
Let’s say the mom is heterozygous for the tongue rolling trait which would make her genotype Tt
               

12. Mom
Dad x
Mom
Dad

13. R r R R r r R r r r r r r R r r r r r r
In flowers red petal color is dominant to white petal color. Cross a heterozygous red petaled flower with a white petaled flower
Rr x rr
Phenotype
50% Red
50% White
Genotype
50% Rr
50% rr R r R R r r R r r r r r r R r r r r r r

14. R r R R R R r R r r r r R R R R R R R R R r r r Rr x Rr Phenotype
75% Red
25% White
Genotype
25% RR
50% Rr
25% rr r R R R R r R r r r r
RR x Rr R R
Phenotype
100% Red
0% White
Genotype
50% RR
50% Rr R R R R R R R r r r

15. R Y R Y y r r y R Y RRYY RRYy RrYY RrYy R RRYy RRyy RrYy Rryy y RrYy
RrYy x RrYy R Y R Y y r r y R Y
RRYY
RRYy
RrYY
RrYy R
RRYy
RRyy
RrYy
Rryy y
RrYy
rrYY
rrYy Y
RrYY r
RrYy
Rryy
rrYy r y
rryy
Phenoype:
9:3:3:1
9 round & yellow, 3 round & green, wrinkled & yellow, 1 wrinkled & green

16. Incomplete Dominance
Sometimes the dominant and the recessive trait blend together. This is called incomplete dominance.
For example in some flowers petal color is incompletely dominant. If you cross a red flower RR with a white flower rr, you would get pink flowers Rr

17. Phenotypic Ratio: 25% red, 50% pink, 25% white
Genotypic Ratio: 25% RR, 50% Rr, 25% rr

18. Your 23rd pair of chromosomes are called your “sex chromosomes”
These chromosomes have the genes that determine if you are male XY or female XX. X Y X X X X Y X X X X Y
Who determines the sex of the child the mom or the dad?
The dad is the only one that can give a Y chromosome so he is the one that determines the sex of the child.

19. Sex linked traits are traits that are on the X chromosome
Some traits are sex linked traits like: colorblindness, hemophilia (a blood disorder), and certain types of baldness.
Sex linked traits are traits that are on the X chromosome
Cross a male who does not have hemophilia with a female carries hemophilia, but does not have it. H Y X H H H H X Y X X X h H h h Y X X X X

20. An example of multiple alleles is blood types.
Some traits are controlled by genes that have more than two alleles this is called a multiple allele.
An example of multiple alleles is blood types.
Blood Type
(Phenotype)
Genotype A
IAIA or IAi B
IBIB or IBi AB
IAIB O ii

21. A I i B A B B I I I I i A i I i i i A I i A i I i i i A i I i i i
Phenotypic Ratio
25% AB
25% A
25% B
25% O A I i B A B B I I I I i A i I i i i A I i
Phenotypic Ratio
50% A
50% O A i I i i i A i I i i i

22. Polygenic Traits Poly – many Genic – genes
Polygenic Traits are traits that are controlled by many genes.
Skin, hair, and eye color are all influenced by the effects from three to six genes.
Each of these genes control the amount of a pigment called melanin. The more of the genes that are expressed, the darker the color produced.

23. http://www. dnalc. org/labcenter/mendeliangenetics/mendeliangenetics_h
Click on “What is Heredity”