1. NON-MENDELIAN INHERITANCE PATTERNS (Modes of Inheritance)
H. Biology
Ms. Kim

2. Review….. What is Complete dominance?
Occurs when the phenotypes of the heterozygote (Hh) and dominant homozygote (HH) are identical
Demonstrates (follows) “Mendelian Genetics”
“Either” “Or”
EXAMPLE:
HH=Tall; Hh=Tall; hh=Tall
HH and Hh are both dominant and hh shows recessive

3. Sometimes…
Inheritance patterns do NOT follow the phenotype patterns (ex: 3:1) that Mendel saw in his pea plants
These patterns are called “Non-Mendelian” Genetic Inheritance Patterns

4. “Non-Mendelian Genetics”
Incomplete (Intermediate) Dominance
1 allele is not completely dominant over the other, so the heterozygote (Hh) has intermediate (or mixed) phenotype between 2 alleles

5. What is Incomplete Dominance?
Incomplete Dominance – type of inheritance when the heterozygous phenotype is a mixture of the two homozygous phenotypes
Example:
Green beta fish (CGCG)
Blue beta fish (CBCB)
Teal beta fish (CGCB)
CBCB x CGCG = teal beta fish
Neither allele is completely dominant or recessive

6. Figure 14.10  1⁄2 P Generation F1 Generation F2 Generation Red CRCR
Gametes CR CW 
White
CWCW
Pink
CRCW
Sperm Cw
1⁄2
Eggs
CR CR
CR CW
CW CW
Figure 14.10

7. Incomplete Dominance Problem #1
If a red four o’clock flower is crossed with a pink four o’clock flower what will their offspring look like?
CRCR = red
CWCW = white
= pink
CRCW
Parent Genotypes 
CRCR x CRCW

8. Perform cross CRCR CRCW CR CW 2 CRCR : 2 CRCW
Genotype ratio:
Phenotype ratio:
KEY
CRCR = red
CWCW= white
CRCW = pink
CRCR
CRCW CR CW
2 CRCR : 2 CRCW
50% Red flowers & 50% Pink!

9. Incomplete Dominance Problem #2
In the four-o’clock plant, homozygous shows the red flower color and homozygous shows the white flower color. Cross a red plant with a white plant and list the genotypic and phenotypic ratios.
CRCR x CW CW
4 CRCW and 100% pink

10. Let’s do some practice problems…
Assume incomplete dominance…
A red gummy bear mates with a yellow gummy bear. Red (R) is dominant. What are the genotype/phenotype ratios of their F1 offspring?
100% Rr 100% orange
If 2 F1 gummy bears from the question above mate. What are the genotype/phenotype ratios of their F2 offspring?
25% RR % Rr % rr
25% Red % orange % yellow

11. “Non-Mendelian Genetics”
Codominance
“Co” means TOGETHER
2 dominant alleles affect phenotype in separate, distinguishable ways
BOTH phenotypes are present
Ex’s of codominance
Speckled flower color
Roan animals (cattle & horses)

12. What is Codominance?
When both the dominant and recessive trait is expressed completely
Neither allele is dominant or recessive
Example: A flower that is homozygous for red flowers (CRCR) is crossed with a plant that is homozygous for blue color (CB CB). The offspring (CR CB) will have spots of blue and spots of red but NO purple
CR CR x CB CB = blue and red spotted
CR CB

13. Roan Animals Show Codominance

14. Codominance Example
In cattle, fur color can either be red (CRCR), white (CWCW) or roan (CRCW).
Roan fur is both red hairs and white hairs together

15. Codominance Example #1 Roan is a coat color found in some cows
= red hair
= red and white hair (Roan)
= white hair
CRCR
CRCw
CwCw
Cross a roan cow with a red cow
Parents = CRCw x CRCR
CR Cw
CRCR
CRCW
CRCw CR
Genotype ratio:
Phenotype ratio:
2 CRCR : 2 CRCW
50% Roan, 50% Red

16. Let’s do some practice problems…
Assume codominance…
A blue flower mates with a yellow flower. Blue (B) is dominant. What are the genotype/phenotype ratios of their F1 offspring?
100% BY 100% Blue AND yellow flowers
If 2 F1 flowers from the question above mate. What are the genotype/phenotype ratios of their F2 offspring?
25% BB % BY % YY
25% Blue 50% blue AND yellow % yellow

17. Multiple Alleles/Codominance
Most genes can be found in more than 2 forms  multiple alleles
A type of inheritance pattern that involves:
3+ alleles that influence gene’s phenotype
4+ phenotypes can occur instead of only 3
Ex: Human Blood type
There are 3 alleles (A,B,O)
We write the alleles:
A = IA
B = IB
O = i
When combined, they create 4 blood phenotypes: A, B, AB, O

18. Table 14.2
The ABO blood group in humans Is determined by multiple alleles (similar to codominance)

19. Blood Type Key A Blood Type B Blood Type
Homozygous Type A  IAIA
Heterozygous Type A  IAi
B Blood Type
Homozygous Type B  IBIB
Heterozygous Type B  IBi
AB Blood Type (codominant) IAIB
AB is the universal receiver
O Blood Type (recessive) ii
O – is the universal donor
O – is the universal donor b/c it lacks all antigens and therefore wont be recognized as foreign
AB+ person's body will not attack red blood cells that carry some, all, or none of the antigens
there is a third antigen called the Rh factor, which can be either present (+) or absent ( – )

20. Blood Type Blood Types of Parents All possible genotypes of parents
All possible genotypes of children
All possible blood types (phenotypes) of children
A & O
IAIA, IAi, ii
IAi, ii
A,O
B & O
A & B
IAIA, IAi, IBIB, IBi
IAIB, IAi, IBi, ii
AB & A
IAIA, IAIB, IAi, IBi
AB, A, or B
AB & B
IAIB, IBIB, IBi
AB & O
IAIB, ii
IAi, IBi
A or B
O & O ii O

21. Blood Type Answers Blood Types of Parents
All possible genotypes of parents
All possible genotypes of children
All possible blood types (phenotypes) of children
A & O
IAIA, IAi, ii
IAi, ii
A,O
B & O
IBIB, IBi, ii
IBi, ii
B,O
A & B
IAIA, IAi, IBIB, IBi
IAIB, IAi, IBi, ii
AB, A, B or O
AB & A
IAIB, IAIA, IAi
IAIA, IAIB, IAi, IBi
AB, A, or B
AB & B
IAIB, IBIB, IBi
IAIB, IAi, IBIB, IBi
AB & O
IAIB, ii
IAi, IBi
A or B
O & O ii O

22. Example Problem
A type AB woman marries a type O man. What are the possible genotypes of their offspring?
Phenotype AB x O
Genotype IAIB x ii
IA IB
Genotype Ratio: 2 IAi: 2 IBi
Phenotype Ratio: 50% A Blood Type
50% B Blood Type i
IAi
IBi

23. Blood Type Practice
What are the possible blood types of a child who's parents are both heterozygous for "B" blood type? 
IBi X IBi 
50% chance IBi, 25% chance IBIB, 25% chance ii
75% chance of B type and 25% chance of O type
What are the chances of a woman with Type AB and a man with Type A having a child with Type O?
IA? x IAIB 
0% chance of Type O b/c mom can’t donate “i” allele
Jill is blood Type O.  She has two older brothers with blood types A & B.  What are the genotypes of her parents?
IAi and IBi

24. Polygenic Inheritance
2 or more genes affect 1 phenotype
“Poly” also means many
“Genic” has to do with genes
Traits that can have a wide range of color
Ex:
Height, skin color, eye color

25. SKIN COLOR: 6 genes involved
AaBbCc
aabbcc
Aabbcc
AaBbcc
AABbCc
AABBCc
AABBCC
20⁄64
15⁄64
6⁄64
1⁄64
Fraction of progeny
SKIN COLOR:
6 genes involved
Figure 14.12

26. Nature and Nurture: The Environmental Impact on Phenotype
Another departure from simple Mendelian genetics  the phenotype depends on environment as well as on genotype
Called multifactorial inheritance
Ex: identical twins looking different
hydrangea flowers