The document discusses several patterns of non-Mendelian inheritance including incomplete dominance, codominance, multiple alleles, and sex-linked traits. These patterns do not follow Mendel's laws of simple dominance and recessive inheritance. Incomplete dominance results in an intermediate phenotype, codominance shows both parental traits simultaneously, multiple alleles involve more than two allele choices for a trait, and sex-linked traits are inherited through the X chromosome.

1. Non-Mendelian Genetics
(Non-Mendelian Patterns of
Inheritance)
-Incomplete dominance
-Codominance
-Multiple Alleles
-Sex-linked traits

2. Non-Mendelian Inheritance
• Some traits don’t follow the simple
dominant/recessive rules that Mendel first
applied to genetics.
• Traits can be controlled by more than one
gene.
• Some alleles are neither dominant nor
recessive.

3. Incomplete Dominance
is a form of intermediate
inheritance in which one
allele for a specific trait is
not dominant over the other
allele.

4. Example

5. Remember!
“With incomplete dominance, a
cross between organisms with
two different phenotypes
produces offspring with a third
phenotype that is a blending of
the parental traits.”

6. Codominance
• Both alleles contribute to the
phenotype of the organism by
showing up simultaneously (at
the same time) in heterozygous
individuals.

7. Example
R = allele for red flowers
W = allele for white flowers
red x white ---> pink
RR x WW ---> 100% RW

8. Remember!
“With codominance, a cross
between organisms with two
different phenotypes produces
offspring with a third
phenotype in which both of the
parental traits appear
together. ”

9. Multiple-Allele Series
• Codominance
• More than two choices of alleles are present for
a trait
• ABO blood type has three alleles
• ABO Blood types:
– If both A and B are present, type is AB
– Neither is recessive
• Individuals can be type A, B, AB, or O
(recessive)

10. Determining Blood Type
• Protein molecules
found on the surface of
RBC’s and in the blood
plasma determine the
blood type of an
individual.
– Antigens are located on
the surface of the red
blood cells
– Antibodies are in the
blood plasma.

11. What are the different blood
groups?
• Blood group A (IA, IA ), (IA, i)
have A antigens on the surface of red
blood cells and B antibodies in blood
plasma.
• Blood group B (IB, IB ), (IB, i)
have B antigens on the surface of red
blood cells and A antibodies in blood
plasma.

12. What are the different blood
groups?
• Blood group AB (IA, IB )
have both A and B antigens on the surface
of red blood cells and no A or B
antibodies in blood plasma.
• Blood group O (i, i)
have neither A or B antigens on the
surface of red blood cells but have both A
and B antibodies in blood plasma.

13. Blood transfusions – who can
receive blood from whom?
• The transfusion will work if a person who
is going to receive blood has a blood
group that doesn't have any antibodies
against the donor blood's antigens.

14. Sex Chromosomes
MALES:
- have non-identical sex
chromosomes (XY).
FEMALES:
- have identical sex
chromosomes (XX).

15. Sex Determination

16. Sex-linked traits
• This is also referred to as “x-linked
traits”.
• These are determined by genes
that are carried on the X
chromosomes.
• This is determined also in the sex
chromosomes of an individual.

17. Genotypes and Phenotypes of
Color Blindness in Humans
Genotypes Phenotypes
1. XX Normal female
2. XX
c
Normal female,carrier of the
gene
3. X
c
X
c
Color-blind female
4. XY Normal male
5. X
c
Y Color-blind male

18. Sex-linked trait

19. Sex-influenced traits
• The traits produced here is not
sex-linked, but is carried by the
body chromosomes or
AUTOSOMES.
– Example of this is Baldness.

20. After doing your activities, do
you now think that Mendel’s
Laws of Inheritance are
incorrect?

21. Video Presentation! 
Why do we need to study other
patterns of inheritance?

22. But wait there's more!
Site some real life situations in
which you can reflect on “Non-
mendelian Genetics”(like: Incomplete
Dominance, Codominance, Multiple
Alleles or Sex linked traits)
You can make a short skit/role play,
rap or a song.

23. Environmental Effects on Gene
Expression
The phenotype of an
organism depends not only on
which genes it has (genotype),
but also on the environment
under which it develops.
Although scientists
agree that phenotype depends
on a complex interaction
between genotype and
environment, there is a lot of
debate and controversy about
the relative importance of
these 2 factors, particularly for
complex human traits.

24. Direction: In ¼ sheet of paper, write FACT if the
statement is correct and BLUFF if it is not.
1. There are traits don’t follow the simple
dominant/recessive rules that Mendel first
applied to genetics.
2. Incomplete dominance supports the “blending
theory of inheritance”.
3. Codominance is the appearance of both of the
parents’ phenotype to offspring.
4. Sex-influence traits are determined by genes
that are carried on the X chromosomes.
5. In ABO blood type, A and B are codominant and
O is recessive.

25. Thank you for
Behaving!
Reported by:
Yannie Doo