This document discusses several types of non-Mendelian genetics inheritance patterns: 1) Incomplete dominance results in a blended phenotype between two traits when hybrids are formed rather than one trait dominating. An example is red and white flowers producing pink hybrids. 2) Codominance occurs when both alleles are fully expressed together in the hybrid phenotype. For example, a black and white cow producing a spotted hybrid. 3) Multiple alleles exist for a single trait, such as multiple coat color alleles in many animals. 4) Polygenic traits are influenced by multiple genes interacting together, like human skin tone. 5) Sex-linked traits involve genes on the sex chromosomes. Examples include color blindness,

1. Non-Mendelian Genetics
Inheritance Concepts Mendel
Never Imagined!

2. Non-Mendelian Genetics
 But, not all inheritance is based on the
rules of Complete Dominance!!

3. Incomplete Inheritance
 The hybrid (heterozygous) offspring
displays a THIRD Phenotype!! Neither trait
is completely dominant, as a result, there
appears to be a blending phenotype.
Red Flower X White Flower = Pink
(RR) (WW) (RW)

4. Incomplete Inheritance Problem
 What is the probability of pink flowers if
pink flowers are bred with red flowers?
50%
chance
of Pink
Flowers

5. Incomplete Inheritance Problem
 What is the probability of white flowers if
pink flowers are bred with pink flowers?

6. CoDominance
 Both traits are dominant, and show up in
the phenotype together. Co means
“together”
 Black Cow X White Cow = Spotted Cow
(BB) (WW) (BW)

7. CoDominance Problem
 What are all the possible phenotypes
when two spotted cows are bred?
Possible
phenotypes
are a black
cow, 2
spotted
cows, and a
white cow

8. Blood Type Inheritance Rules:
1. A person with the IA allele
will have A carbohydrates.
2. A person with the IB allele
will have B carbohydrates.
3. A person with the recessive
i allele will have no
carbohydrates.
4. Or a person with both IA and
IB alleles will have both A
and B carbohydrates on
their cells.
Cells Genotypes Blood types
IAi, IAIA Type A
blood
IBi, IBIB Type B
blood
IAIB Type AB
blood
ii Type O
blood

9. Blood Type Problems
If a woman with AB blood
has children with a man
who has type O, what will
be the possible genotypes
of their children? What will
be their blood types?
IA IB
i
i
IA i
IA i
IB i
IB i

10. Blood Type Problems
Blood Type Problem 2: A
woman with type B blood
has a child with type O
blood. How is this possible
if her husband has type A
blood?

11. Multiple Alleles
 When more than 2 varieties exist in a trait.
Many animals have a variety of coat
colors.

12. Polygenic Traits
Require more than one gene (allele) to
determine trait.
Skin tone is determined by 4-6 genes—that
means that there may be six different
chromosomes involved!

13. Sex-linked Inheritance
 Genes for some traits are found on the sex
chromosomes (X or y)
 Most of these traits are recessive the normal
gene is dominant
 Heterozygous Females (XXc) are carriers. They
do not show the trait, but carry a gene for the
trait.
 Homozygous Females (XcXc) have the trait
 Males with the gene (XcY) have the trait.—They
do not have another X to counterbalance the
affected gene

14. Color blindness is a sex-linked
recessive trait. The gene for this trait is
inherited through the X chromosome.
If a woman with normal vision
has children with a man
who is colorblind,
what are the chances
that their children will be
colorblind?
Will any children be carriers
of the trait?
Xc Y
X
X
XXc
XXc
XY
XY

15. Non-Mendelian Genetics
What are the similarities and differences
between each of these forms of inheritance?
How will you remember? What are
examples of each type?
 Incomplete inheritance
 CoDominance
 Multiple Alleles
 Polygenic Traits
 Sex-linked inheritance