The document provides an overview of non-Mendelian genetics, discussing patterns of inheritance that do not follow Mendel's laws, such as incomplete dominance, codominance, and multiple alleles. It explains how traits can be influenced by more than one gene and the effects of different alleles on phenotypes, using examples like flower colors in snapdragons and human blood types. Inheritance patterns with blood types are illustrated with a case involving Charlie Chaplin and a paternity dispute, highlighting the implications of blood type genetics.

1. NON-
MENDELIAN
PATTERNS OF INHERITANCE

2. OVERVIE
W
TOPICS
• Law of Incomplete
Dominance
• Law of Codominance
• Law of Multiple Allelism

3. MENDELIAN VS NON-
MENDELIAN GENETICS
• Mendelian traits are determined by dominant and
recessive alleles of one gene.
• Non-Mendelian traits are not determined by
dominant and recessive alleles and can be governed
by more than one gene.

4. NON-MENDELIAN
GENETICS
It involves the pattern of inheritance that does not
follow Mendel’s laws.

5. It is not determined by dominant and recessive alleles
but governed by more than a single gene.

6. INCOMPLE
TE
DOMINAN
CE
The heterozygote displays a
phenotype that is an
intermediate between the
phenotypes of both
homozygote parents.

7. In snapdragon plant, if a homozygous white flower is
crossed with a homozygous red flower, a pink flower is

9. Chestnut brown Creamy white
Palomino
X

10. Sometimes, neither of a pair of alleles is completely
dominant or completely recessive. Instead of one of
them completely hiding the effect of the other in a
heterozygote, they both have an effect on the
phenotype. This is called codominance.
The result is that there can
be three different
phenotypes.

11. CODOMINA
NCE
Occurs when the phenotypes of
both parents are
simultaneously expressed in the
same offspring.

13. Most of the genes exist in two alternative forms having
different phenotypic effects called alleles which occupy
the same locus in the homologous chromosome.

14. However, there are several
genes that exist in more
than two alternative forms
called multiple alleles,
which control alternative
forms of the same character
and they occupy the same
locus in a pair of
homologous chromosomes.

15. MULTIPLE
ALLELES
Refers to the existence of more
than two different alleles for a
single gene in a population.

16. These alleles can have various effects on an organisms phenotype.

17. • Four alleles exist for the c gene.
• The wild-type version, C+C+, is
expressed as brown fur.
• The chinchilla phenotype, cchcch,
is expressed as black-tipped white
fur.
• The Himalayan phenotype, chch,
has black fur on the extremities
and white fur elsewhere.
• The albino, or “colorless”
phenotype, cc, is expressed as
white fur.

18. • In cases of multiple alleles, dominance hierarchies can exist.
• In this case, the wild-type allele is dominant over all the others,
chinchilla is incompletely dominant over Himalayan and albino, and
Himalayan is dominant over albino.
• This hierarchy, or allelic series, was revealed by observing the
phenotypes of each possible heterozygote offspring.

19. Inheritance of A, B, AB and O Blood Group - an example of
codominance

20. • In humans, there are 4 blood types (phenotypes): A, B, AB, and O.
• Blood type is controlled by 3 alleles: IA, IB, IO (the base letter = I
stands for immunoglobulin).

23. Can a child with blood type O be produced
from parents with blood types A and B?

24. What blood types are possible among the children
of a cross between a man who is blood type A and
a woman of blood-type B?

25. In 1941, Charlie Chaplin met a young actress named, Joan
Barry with whom he had an affair. The affair ended in
February 1942 but 20 months later, Barry gave birth to a
baby girl and claimed that Chaplin was the father. Barry
then sued for child support. At this time, blood typing had
just come into widespread use, and Chaplin’s attorney had
Chaplin, Barry, and the child blood-typed. Barry had blood
type A, her child had blood type B and Chaplin had blood
type O. Could Chaplin have been the father of Barry’s
child?

26. A mother and her child have blood type O. Which blood
group can the father NOT belong to?

27. THANK
YOU