1. Ch. 11 Notes - Genetics

2. I. Who was Gregor Mendel?
A. Gregor Mendel - Austrian monk who studied how traits are inherited; known as the “Father of Genetics”
1. Genetics - branch of biology that studies heredity
a. Heredity - passing on of traits from parent to offspring

3. I. Who was Gregor Mendel? B. Mendel’s Experiments
1. Studied/Researched on pea plants
a. They have many traits such as flower color (purple or white), peas (round or wrinkled), pea color (yellow or green) and height (tall or short).

4. I. Who was Gregor Mendel?
Short pea plant
Tall pea plant
All tall pea plants
3 tall: 1 short P1 F1 F2
b. Mendel bred a tall pea plant with a short plant (P generation).
c. The offspring in the 1st generation (F1 generation) were all tall.

5. I. Who was Gregor Mendel? d. Then, he bred two of the F1 plants.
Short pea plant
Tall pea plant
All tall pea plants
3 tall: 1 short P1 F1 F2
d. Then, he bred two of the F1 plants.
e. The offspring in the 2nd generation (F2 generation) were 75% tall and 25% short.
f. The short trait disappeared in the 1st generation and reappeared in the 2nd generation.

6. I. Who was Gregor Mendel?
Short pea plant
Tall pea plant
All tall pea plants
3 tall: 1 short P1 F1 F2
2. Mendel discovered that each trait is controlled by alleles.
a. Alleles: forms/versions of the same gene
Each person has TWO alleles for each gene; 1 from mother and 1 from father.
Ex: T = the allele for tall; t = the allele for short

7. I. Who was Gregor Mendel? Some alleles are dominant and recessive
Dominant - a trait that is always expressed (seen) in an individual if the allele is present (capital letter)
Ex: T = tall allele
Recessive - a trait that is hidden by the dominant allele; expressed only when two copies of the recessive allele are inherited (lowercase letter)
Ex: t = short allele

8. I. Who was Gregor Mendel?
Individuals can be described by their genotype and phenotype
Genotype - genetic makeup (letters); alleles present in an individual
Ex: TT, Tt, tt
Type of Genotypes:
Homozygous - two of the SAME alleles for a trait
Ex: TT or tt
Heterozygous (hybrid) - two DIFFERENT alleles for a trait
Ex: Tt

9. I. Who was Gregor Mendel? TT, Tt=tall tt=short
Phenotype - physical appearance; what traits are expressed in the individual
Ex: tall or short plants
TT, Tt=tall tt=short

10. II. Punnett Squares/Test Crosses
A. Punnett Square/Test Cross - a tool used to predict the alleles/traits present in offspring
1. When parents produce gametes (sperm or eggs), their genes separate to produce haploid cells
a. Each gamete contains ONE allele
Homozygous Tall Dad
Heterozygous Tall Dad
Homozygous Short Dad T T T t t t

11. II. Punnett Squares/Test Crosses
B. How to Solve a Monohybrid Cross
1. Determine the genotypes (letters) of the parents.
2. Set up the punnett square with one parent on top and one parent on the side.
3. Fill out the Punnett square boxes (Look up and over to the left to fill them in).
4. Analyze the probability (likelihood) that the offspring would possess each specific trait.

12. II. Punnett Squares/Test Crosses
C. Practice
Y = yellow pea color; y = green pea color
1. Cross two heterozygous pea plants.
Parent 1 Genotype __________ Parent 2 Genotype __________
What is the chance of the offspring having yellow pea color?
Genotypic Ratio:
YY : Yy : yy
Phenotypic Ratio:
yellow : green

13. II. Punnett Squares/Test Crosses
Y = yellow pea color; y = green pea color
2. Cross a homozygous recessive pea plant with a heterozygous pea plant.
Parent 1 Genotype __________ Parent 2 Genotype __________
What is the chance of the offspring having yellow pea color?
Genotypic Ratio:
YY : Yy : yy
Phenotypic Ratio:
yellow : green

14. II. Punnett Squares/Test Crosses
Y = yellow pea color; y = green pea color
3. Cross a homozygous recessive pea plant with a homozygous dominant pea plant.
Parent 1 Genotype __________ Parent 2 Genotype __________
What is the chance of the offspring having yellow pea color?
Genotypic Ratio:
YY : Yy : yy
Phenotypic Ratio:
yellow : green

15. II. Punnett Squares/Test Crosses
D. How to Solve a Dihybrid Cross
1. Determine parent genotypes (letters).
2. Determine gamete combinations from mom and dad. (FOIL method from math class - Use arrows!)
3. Write the gametes from mom on 1 side of the square and dad on the other side.
4. Fill in the boxes in the punnett square (look up and to the left).
5. Analyze the probability (likelihood) that the offspring would possess the specific traits.

16. II. Punnett Squares/Test Crosses
PRACTICE:
R = round peas, r = wrinkled peas
Y = yellow pea color; y = green pea color
Cross two heterozygous round yellow pea plants.
Parent 1 Genotype _____ Parent 2 Genotype _____
Parent Gamete Possibilities: FOIL
Parent #1 Gametes: RY, Ry, rY, ry
Parent #2 Gametes:  RY, Ry, rY, ry

17. What is the chance of the offspring having round and yellow peas?Ry RY rY ry RY Ry rY ry

18. III. Special Inheritance
A. Autosomes pairs of body chromosomes in a human
22 Autosomes
Sex chromosomes

19. III. Special Inheritance
B. Sex chromosomes pair of chromosomes in a human; the last pair in a karyotype
a. Ex. XX-female XY- male
22 Autosomes
Sex chromosomes

20. III. Special Inheritance
Show a punnett square crossing male and female sex chromosomes.
d. Every time a male and female have a baby, what is the chance of them having a son? A daughter?
e. If a female has 5 sons in a row, what is the chance of her having another son? A daughter?
f. Which parent determines the sex of the child? WHY?

21. III. Special Inheritance
C. Sex-Linked Traits - traits located on the sex chromosomes (usually the X chromosome)
a. Dad gives X chromosome to daughters and Y chromosome to sons
b. Mom gives X chromosome to daughters and sons
If a male inherits a sex-linked trait, which parent(s) gave him the trait?
MOM
If a female inherits a sex-linked trait, which parent(s) gave her the trait?
MOM OR DAD
Who (males or females) is most likely to inherit a sex-linked trait? WHY?
Males – they only need to inherit ONE X chromosome

22. III. Special Inheritance
c. Examples in humans
Male pattern baldness
Red/green colorblindness
Hemophilia (problems with blood clotting)
Muscular Dystrophy (muscle weakness, loss of muscle tissue)

24. III. Special Inheritance
d. Other Examples
Eye color in Drosophila (fruit flies)
R = Red eye Color; r = white eye color
Cross white eyed male (XrY) with red eyed female (XRXR)
What percentage of offspring are likely to have red eyes?
What percentage of male offspring are likely to have red eyes?
What percentage of female offspring are likely to have red eyes?

25. III. Special Inheritance
Examples
Eye color in Drosophila (fruit flies)
R = Red eye Color; r = white eye color
Cross white eyed male (XrY) & heterozygous red eyed female (XRXr)
What percentage of offspring are likely to have red eyes?
What percentage of male offspring are likely to have red eyes?
What percentage of female offspring are likely to have red eyes?

26. IV. Not all traits are controlled by simple dominant and recessive alleles!
A. Incomplete Dominance - heterozygous individuals display an intermediate (blending) phenotype of the two homozygous individuals
1. Examples in humans
Hair texture
SS = straight
CC = curly
SC = wavy
Tay Sachs Disease (inability to produce enzyme that breaks down lipids)
EE = produces enzyme
NN = does not produce enzyme
EN = produces half amount of enzyme

27. IV. Not all traits are controlled by simple dominant and recessive alleles!
2. Other Examples
Flower color in snapdragons
RR = Red, WW = white, RW = pink
Cross a red flower with a white flower.
Parent 1 Genotype ______ Parent 2 Genotype _____
What is the chance of producing a pink flower?
Genotypic Ratio:
RR : RW : WW
Phenotypic Ratio:
red: pink: white

28. Cross a pink flower with a pink flower.
III. Not all traits are controlled by simple dominant and recessive alleles!
Cross a pink flower with a pink flower.
Parent 1 Genotype _____ Parent 2 Genotype _____
What is the chance of producing a white flower?
Genotypic Ratio:
RR : RW : WW
Phenotypic Ratio:
red: pink: white

29. III. Not all traits are controlled by simple dominant and recessive alleles!
B. Co-dominance - heterozygous individuals display BOTH traits of the two homozygous individuals
1. Examples in humans
Sickle Cell Anemia (abnormally shaped red blood cells)
NN = normal shaped cells
SS = sickle shaped cells
NS = normal and sickled shaped cells
Blood Type
Type A
Type B
Type AB

30. ***** Special Inheritance *****
Hemoglobin—protein that carries oxygen in blood, makes blood red
In homozygous recessive individuals—hemoglobin is defective and makes blood cells sickle (half moon) shaped
These blood cells—cause slow blood flow, block small vessels, tissue damage and pain
In heterozygous individuals – both normal and sickled hemoglobin are produced
They produce enough normal hemoglobin that they do not have serious health problems

32. Genotypic Ratio: BB: BW : WW Phenotypic Ratio:
IV. Not all traits are controlled by simple dominant and recessive alleles!
2. Other Examples
Coat color in chickens
BB = black
WW = white
BW = black AND white speckled
Cross a black rooster with a white chicken.
Parent 1 Genotype _____ Parent 2 Genotype _____
What is the chance of producing black and white chicks?
Genotypic Ratio:
BB: BW : WW
Phenotypic Ratio:
black: black/white: white

33. IV. Not all traits are controlled by simple dominant and recessive alleles!
Complete the last cross on your own. Be ready to discuss.

34. V. Blood Type (codominance in humans)
A. An example of multiple alleles – more than one allele controls the trait
B. It is determined by the presence or absence of proteins (chains of amino acids) on the surface of red blood cells
a. Mixing incompatible blood types can cause blood clots, which can result in death

35. V. Blood Type (codominance in humans)
Human Blood Types
Phenotype
Genotype
Blood cell surface molecules (antigens)
Type A
IAIA or IAi
A antigens
Type B
IBIB or IBi
B antigens
Type AB
IAIB
A and B antigens
Type O ii
No antigens

36. V. Blood Type (codominance in humans)

37. V. Blood Type (codominance in humans)
C. Alleles IA and IB – are co-dominant to each other
D. Allele i –is recessive to both IA and IB
a. Type O blood — universal donor
Has no proteins on the blood cells so any blood type can receive it
b. Type AB blood — universal acceptor
Has both proteins on blood cells so this blood type can receive any blood

38. V. Blood Type (codominance in humans)
E. Cross parent with A ( IAi) blood with a parent with B blood (IBi).
Genotypic ratio
0 IA IA :
1 IA i :
0 IB IB :
1 IB i :
1 IA IB :
1 ii
IA i
IBi
IAIB IB i
IAi ii
Phenotypic ratio (blood type)—
1 type AB : 1 type A : 1 type B : 1 type O

39. VI. Rh Factor – describe the presence or absence of another protein on blood cells.
A. Rh Positive = have proteins
a. Genotypes: Rh+/Rh+ or Rh+/Rh-
B. Rh Negative = no proteins
b. Genotype: Rh-/Rh-

40. Rh+ Rh- Rh- Rh+/Rh- Rh-/Rh- Rh+/Rh- Rh-/Rh-
VI. Rh Factor – describe the presence or absence of another protein on blood cells.
C. Cross parent heterozygous for the Rh factor with another parent who does not have the Rh factor.
Rh Rh-
Rh-
Rh+/Rh-
Rh-/Rh-
Rh-/Rh-
Rh+/Rh-
Genotypic ratio
0 Rh+/Rh+ : 2 Rh+/Rh-: 2 Rh-/Rh-
Phenotypic ratio
2 Rh positive: 2 Rh negative