1. Complex Patterns of Inheritance
Genetics 2
Complex Patterns of Inheritance

2. How do we get blended traits?
Incomplete dominance
________________________- The dominant allele will not fully cover up a recessive allele and the trait will be a result of the two blending or mixing together.

3. How do we get blended traits?
In carnations, incomplete dominance can be seen in flower color:
red (RR) pink (Rr) white (rr)
1. Cross two pink carnations
______x______ Rr Rr
Possible genotypes of offspring:
Possible phenotypes of offspring:
R r
RR= ¼
Rr= 2/4
Rr=1/4
RR Rr
Rr rr R r
Red= ¼
Pink= 2/4
White= ¼

4. How do we get blended traits?
2. Cross a red and a pink carnation:
_______x_______
Possible genotypes of offspring:
Possible phenotypes of offspring: RR Rr
RR: 2/4
Rr: 2/4
R R
Red: 2/4
Pink: 2/4 R r
RR RR
Rr Rr

5. Practice Problems: Incomplete Dominance
List all possible phenotypes and the corresponding genotype for hair texture.
_______________________________________
In humans, hair texture is due to an incompletely dominant trait. Straight hair (H) is incompletely dominant to curly hair (h). When crossed, they produce a heterozygous individual with wavy hair (Hh).
Straight (HH), Wavy (Hh), and Curly (hh)

6. Practice Problems: Incomplete Dominance
Using a Punnett square, cross a curly-haired person with a wavy-haired person. hh Hh
HH: 0/4
Hh: 2/4
hh: 2/4
Straight: 0/4
Wavy: 2/4
Curly: 2/4
h h H h
Hh Hh
hh hh
0:2:2
What is the genotypic ratio of the offspring? ________________________
What is the phenotypic ratio of the offspring? _______________________
0:2:2

7. Practice Problems: Incomplete Dominance
In guinea pigs, white fur (F) is incompletely dominant over yellow fur (f). When crossed they produce heterozygous offspring with cream-colored fur (Ff).
List all possible phenotypes and the corresponding genotype for fur color.
_______________________________
White: FF Cream: Ff yellow:ff

8. Practice Problems: Incomplete Dominance
Using a Punnet Square, cross two guinea pigs with cream-colored hair. Ff
_______________ X __________________
Show your lists of genotypes & phenotypes here!
F f
Genotypes:
FF:
Ff:
ff:
Phenotypes:
White:
Cream:
Yellow: F f
FF Ff
Ff ff
2/4
2/4
What is the genotypic ratio of the offspring? ________________________
What is the phenotypic ratio of the offspring? _______________________
1:2:1

9. Can we express 2 traits at once?
Codominance - When two different alleles are expressed __________ , at the same time (neither one is recessive).
equally

10. Can we express 2 traits at once?
Codominant alleles are written as capital letters with superscripts or subscripts (HR or B1). Since the trait is inherited from both parents, it is important to still use two ‘sets of letters’ as seen below:
The allele for red hair (HR) is codominant with the allele for white hair (HW) in cattle. Cattle that have the genotypes HRHW are called roan because their hair is a mixture of red and white hairs.

11. Can we express 2 traits at once?
HRHR = Red HRHW = roan HWHW = White
Cross a red cow and a white bull:
Possible genotypes of offspring:
2. Possible phenotypes of offspring:
HR HR HW
HRHR :
HRHW:
HWHW:
0/4
4/4
HRHW
HRHW
Genotypic Ratio:
0:4:0
HRHW
HRHW
Red:
Roan:
White: 4
Phenotypic Ratio:
0:4:0

12. Can we express 2 traits at once?
HRHR = Red HRHW = roan HWHW = White
Cross a roan cow and a roan bull:
HR HW
A. Possible genotypes of offspring:
  B. Possible phenotypes of offspring:
HRHR:
HRHW:
HWHW:
1/4
2/4 HR HW
Genotypic Ratio:
1:2:1
HRHR HRHW
HRHW HWHW
1/4
2/4
Red:
Roan:
White:
Phenotypic Ratio:
1:2:1

13. What are some examples of Codominance in humans?
In humans, red blood cells contain a protein called hemoglobin. It is the hemoglobin that gives the red blood cell its color and ability to pick up oxygen and carry to other cells.

14. What is Sickle Cell Anemia?

15. How is sickle cell anemia inherited?
sufferers
Sickle cell _________ are homozygous (HSHS)
Because all of their blood cells are affected by the sickle cell gene, these people are severely afflicted by the disease. Their red blood cells can becomes sickle shaped, rigid and live about 20 days. They also tend to get stuck in narrow blood vessels, which may cause complications.

16. How is sickle cell anemia inherited?
carriers
Sickle cell ___________ are heterozygous (HAHS)
These carriers produce normal blood cells and sickle cell blood cells. Usually these people do not experience severe affects of this disease.
Sickle cell anemia is more common in some parts of the world because being a carrier causes Malaria resistant. In places where Malaria is a problem, having 1 copy of the sickle cell gene is beneficial.

17. How is sickle cell anemia inherited?
normal
Cells with _________ hemoglobin (no sickle cell anemia) are homozygous (HAHA)
Their red blood cells are disk shaped, soft/flexible and live for about 120 days.

18. How is sickle cell anemia inherited?
Complete a punnett square to determine the chances of two sickle cell carriers having a homozygous normal child?
Genotype of parents: ________ x ___________
HAHS
HAHS
HA HS HA HS
HAHA
HAHS
HAHA:
¼ Normal
HAHS:
2/4 Carriers
HAHS
HSHS
HSHS:
¼ Sufferer
25%

19. Practice Problems: Codominance pg. 7
In horses, pale cream color (C) is codominant to chestnut color (C). When crossed, they produce a heterozygous individual called a palomino (C C) which has a cream & chestnut coat.
List all possible phenotypes and the corresponding genotype for coat color. ___________________________________________
Pale (CC) Palomino (CC’) Chesnut (C’C’)

20. Practice Problems: Codominance pg. 7
Using a Punnett square, cross a palomino horse with another palomino horse.
CC’
______x_______
C C’
Show your lists of genotypes & phenotypes here! C C’ CC
CC’
CC= ¼ Pale
CC’= 2/4 Palomino
CC’
C’C’
C’C’= ¼ Chesnut
1:2:1
What is the genotypic ratio of the offspring? _______
1:2:1
What is the phenotypic ratio of the offspring? ______

21. Practice Problems: Codominance pg. 7
In chickens, black feather color (FB) is codominant to white feather color (FW). The heterozygous individual is a combination of black and white feathers that results in a checkered pattern (FBFW).
List all possible phenotypes and the corresponding genotype for feather color.
_________________________________________
Black (FB FB ), Checkered (FBFW) White (FWFW )

22. Practice Problems: Codominance pg. 7
Using a Punnett square, cross a checkered chicken with a black chicken.
_____x_____
FBFW
FB FB
FB FW
Show your lists of genotypes & phenotypes here! FB
FB FB
FBFW
FB FB : 2/4 Black
FBFW: 2/4 Checkered
FB FB
FBFW
FWFW: 0/4 White
2:2:0
What is the genotypic ratio of the offspring? _________
2:2:0
What is the phenotypic ratio of the offspring? _________

23. Are all traits controlled by only 1 gene?
What are some examples of traits you can think of that have a range of phenotypes?
Eye color:
Blue, Green, Brown, Hazel

24. Are all traits caused by only 1 gene?
What are some examples of traits you can think of that have a range of phenotypes?
Hair color:
black to blonde and everything in between.

25. Are all traits caused by only 1 gene?
Polygenic Traits are controlled by the interaction of more than one gene. In humans, there are several obvious examples of polygenic traits such as hair color, eye color, height and skin tone. Traits that are polygenic tend to show great degrees of variation.

26. Are all traits caused by only 1 gene?
Skin color is caused by at least 3 different genes that code for the production of pigment. The more dominant genes that you have, the more pigment is produced (and therefore the darker your skin).

27. Are all traits caused by only 1 gene?
If two parents have a moderate skin tone (AaBbCc), the graph below shows the probability of having a child with each skin tone.
aabbcc aabbCC AaBbCc AABbCc AABBCC
Lightest skin tone Darkest skin tone