1. Heredity not following the Rules
Learning Goal:
predict possible outcomes of various genetic combinations such as non-Mendelian inheritance

3. Incomplete dominance=Blending
A heterozygous condition in which both alleles are partially expressed, often producing an intermediate or blended phenotype (which is different than either of the homozygous forms).
Snapdragons

4. so they blend their strengths together make a new color.
Incomplete dominance
so they blend their strengths together make a new color.
Both traits are "weak"
Snapdragons

5. Incomplete dominance RR R’R’ RR’ RR RR’ RR’ R’R’ In Incomplete
use the SAME
letters since they
both are weak!
Incomplete dominance RR
R’R’
RR’ RR
RR’
RR’
R’R’

6. Incomplete dominance H’ H’ H H
Palomino horses are a cross between a chestnut horse and a cremello (white) color horse.
Practice the cross using a Punnett Square. H’ H’
HH’ H H

7. Codominance=Both Show
Codominance –Both phenotypes are dominant. Instead, the heterozygous individual expresses both phenotypes.
Co – both are dominant enough to be expressed!!
Dominique chickens

8. Predict the outcome if BOTH chickens are dominique
In CODOMINANCE,
use DIFFERENT
letters since they
both are strong!
Codominance
BB - Black
WW - White
BW - Black and White W W
Predict the outcome if BOTH chickens are dominique
(black and white) ???? BW
Cross a black chicken with a white chicken and what to you get if the traits are CODOMINANT? B B

9. BB=1 BW=2 WW=1 Codominance B W B W BB BW WW BB - Black WW - White
BW - Black and White B W BB BW WW B
BB=1
BW=2 W
WW=1

10. Codominance
Another example of codominance is ABO blood typing. The blood types A and B are codominant to each other; however, type O is actually recessive to A and B.

11. When both alleles exist,
Codominance
IBIB or IBi ii
IAIB
IAIA or IAi
When both alleles exist,
both are present!

12. Codominance Universal recipient Universal donor Blood Group Antibodies
Which group is the
universal recipient?
Which group is the
universal donor?
Codominance
Blood Group
Antibodies
Can give blood to…
Can receive blood from AB
None
A, B, AB, and O A B
A and AB
A and O
B and AB
B and O O
A and B
Universal
recipient
Universal
donor

13. Practicing Blood Types
A man of blood type IAIA marries a woman with blood type IAIB. What is the chance they will have a child with type IAIB blood? IA IB
IAIA
IAIB IA
AB? IA

14. Practicing Blood Types #2
There could be
2 genotypes
for the man:
BB or BO
Practicing Blood Types #2 O?
A man of blood type B marries a woman with blood type O. What is the chance they will have a child with type O blood? i i i i
IBi
IBi ii IB IB 0%
50% IB i

15. Codominance Blood Group Antigens Antibodies Can give blood to…
Can receive blood from AB
A and B
None
A, B, AB, and O A B
A and AB
A and O
B and AB
B and O O

16. Multiple Alleles Why can you only have 2 genes for each trait?
Each individual can only have 2 homologous chromosomes thus 2 alleles for a trait, but there could be more than 2 alleles present in a population. This type of inheritance is known as multiple alleles.
Why can you only have 2 genes for each trait?
Because… you only have 2 of each type of chromosome!!

17. Multiple Alleles - examples
Blood Type is an example of a trait that has multiple alleles. There are 3 possible alleles that could be inherited – A, B, and O, but you can only inherit 2 of them.
Coat color in rabbits is inherited as a series of multiple alleles.

18. Multiple Alleles - examples
How many alleles
are there for
rabbit coat color? 4

19. Multiple Alleles - examples
Why is dark gray
a capital C?
What are all of the possible genotypes for a
dark-gray coated rabbit? (4)
CC Ccch Cch Cc
chinchilla rabbit (3)
cchcch cchch cchc
Himilayan rabbit(2)
chch chc
White rabbit (1) cc

20. Multiple Alleles - examples
Predict the phenotype for a rabbit with a cchch.
Chinchilla
Is it possible to obtain a white rabbit if one parent is white and the other is chinchilla?
Yes. Only if the chichilla is cchc

21. Polygenic Inheritance
Polygenic inheritance is the inheritance pattern of a trait that is controlled by two or more genes. The genes may be on the same chromosome or on different chromosomes.
Height in humans
Skin color

22. Polygenic Inheritance
Gametes
 ABC 
 ABc 
 AbC 
 Abc 
 aBC 
 aBc 
 abC 
 abc 
ABC 6 5 4 3
ABc 2
AbC
Abc 1
aBC
aBc
abC
abc
Polygenic inheritance in people showing a cross between two bi-racial parents (AaBbCc x AaBbCc). Skin color is controlled by 3 different genes. The offspring contain seven different shades of skin color based on the number of capital letters in each genotype.
Skin color

23. Sex-Linked Inheritance
X and Y Chromosomes are sex chromosomes
Remember that genes are located on chromosomes
XX are female and XY are male

24. Sex-Linked Inheritance
X and Y Chromosomes
The X and Y chromosome carry different genes, so they are NOT homologous.

25. Sex-Linked Inheritance
How Sex is Determined
Treat the cross the same as a monohybrid
Father has genotype XY
Mother has genotype XX
The chance of
each sex being
born is 50% X X XX XY X Y

26. Sex-Linked Inheritance
Traits found only on the X chromosome only are called sex-linked
Males will only have one copy of this gene, either the dominant or recessive form
Females will have two copies, and can be homozygous dominant, heterozygous, or homozygous recessive

27. Sex-Linked Inheritance
Sex-linked genes
The Y chromosome is missing this portion of the X chromosome
X chromosome contains over 2300 genes
Y chromosome contains only 25 genes, including the sex-determining gene SRY
SRY directs the formation of male anatomy

28. Sex-Linked Inheritance
Sex-Linked Crosses
Write alleles so X is shown with a superscript for the trait (XH Xh)
Y has no superscript (Y)
Females who are heterozygous for a recessive trait are called carriers – they will not show the trait, but can pass it to offspring

29. Sex-Linked Inheritance
Sex-linked crosses Practice Problem
Hemophilia, a disease where blood does not clot properly, is caused by a recessive sex-linked allele. A female, who is a carrier for hemophilia and a normal male have a child. What is the probability that the child will be born with hemophilia? XH Xh
XHXH
XHXh
XH Y
XhY
25%
chance XH Y

30. Hemophilia inheritance

31. POPQUIZ!! (Just kidding)
A roan cow is the product of a red cow and a white cow. What type of inheritance is exhibited?
Complete dominance
Codominance
Incomplete dominance
Sex-linked
Multiple alleles
Polygenic B

32. POPQUIZ!! C Complete dominance Codominance Incomplete dominance
Curly haired people have the genotype HH, while straight haired people have the genotype hh. A wavy haired person is heterozygous. What type of inheritance does this exhibit?
Complete dominance
Codominance
Incomplete dominance
Sex-linked
Multiple alleles
Polygenic C

33. POPQUIZ!!
How well a person performs on an IQ test is controlled by multiple genes. Which of the following types of inheritance does this exhibit?
Complete dominance
Codominance
Incomplete dominance
Sex-linked
Multiple alleles
Polygenic F

34. POPQUIZ!!
Hair loss is a trait caused by a gene located on the X chromosome. This trait would be considered -
Complete dominance
Codominance
Incomplete dominance
Sex-linked
Multiple alleles
Polygenic D

35. BTW

36. POPQUIZ!!
Kim has always wondered why her 2nd toe is longer than her first. She recently discovered that it is a dominant trait. This trait is considered to exhibit -
Complete dominance
Codominance
Incomplete dominance
Sex-linked
Multiple alleles
Polygenic A

37. POPQUIZ!!
Here is an easy one! Blood types fall under the category of which type of inheritance?
Complete dominance
Codominance
Incomplete dominance
Sex-linked
Multiple alleles
Polygenic E A B
HEE HEE