Non-Mendelian Genetics(Non-Mendelian Patterns of

Inheritance)-Incomplete dominance

-Codominance-Multiple Alleles

-Sex-linked traits

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.

Incomplete Dominance

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

Example

Remember!

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

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

Example

R = allele for red flowers

W = allele for white flowers

red x white ---> pink

RR x WW ---> 100% RW

Remember!

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

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)

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.

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.

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.

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.

Sex Chromosomes

MALES:

- have non-identical sex chromosomes (XY).

FEMALES:

- have identical sex chromosomes (XX).

Sex Determination

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.

Genotypes and Phenotypes of Color Blindness in Humans

Genotypes Phenotypes

1. XX Normal female

2. XXc

Normal female,carrier of the

gene

3. XcX

cColor-blind female

4. XY Normal male

5. XcY Color-blind male

Sex-linked trait

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.

After doing your activities, do

you now think that Mendel’s

Laws of Inheritance are

incorrect?

Video Presentation!

Why do we need to study other

patterns of inheritance?

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.

Environmental Effects on Gene

ExpressionThe 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.

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.

Thank you for Behaving!

Reported by: Yannie Doo