NonMendelian Genetics

Non-Mendelian Traits

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Incomplete Dominance and Codominance

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Incomplete Dominance

Shows in the heterozygous or hybrid individual.
** 2 alleles blend to give an "blended" or "mixed" appearance.

Example: Snapdragons
red (RR) x white (rr)
RR = red flower
rr = white flower

R

R

r

r

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Incomplete Dominance

All offspring are Rr = pink
(heterozygous
pink)

Produces the
F1 generation

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Incomplete Dominance

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Multiple Choice

What is incomplete dominance?

• A genetic situation in which one allele is completely recessive

• A genetic situation in which one allele does not completely dominate the other allele, and therefore results in a new phenotype that is a blend of the two alleles.

• A genetic situation in which both alleles are equally expressed

• A genetic situation in which one allele completely dominates the other allele

Multiple Choice

Give an example of incomplete dominance in humans.

• Example: In humans, the inheritance of blue eyes (dominant) and brown eyes (recessive) results in individuals with green eyes, which is an intermediate phenotype.

• Example: In humans, the inheritance of curly hair (dominant) and straight hair (recessive) results in individuals with wavy hair, which is an intermediate phenotype.

• Example: In humans, the inheritance of dimples (dominant) and no dimples (recessive) results in individuals with small dimples, which is an intermediate phenotype.

• Example: In humans, the inheritance of semi-attached earlobes (dominant) and free earlobes (recessive) results in individuals with attached earlobes, which is an intermediate phenotype.

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Codominance

Two or more alleles are expressed/shown in heterozygous individuals.

Example: Chicken feathers

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Codominance

Another Codominance Example

Blood type:

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Codominance Problem

Example: male Type B (IBIB) x female Type A (IAi)

1/2 = IAIB

1/2 = IBi

Multiple Choice

Explain codominance and provide an example.

• An example of codominance is the ABO blood group system, where the A and B alleles are both fully expressed, resulting in the AB blood type.

• Codominance occurs when both alleles are completely suppressed, resulting in no expression of either allele.

• Codominance is when one allele is completely dominant over the other, resulting in only one allele being expressed.

• An example of codominance is the blending of red and white flowers to produce pink flowers.

Multiple Alleles

Genes with 3 or more alleles may determine a trait.

Example: ABO blood types

-A & B are co-dominant, O is
recessive.

-Possible blood types: O,A,B,AB

VideoAmeoba Sisters Multiple Alleles

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Multiple Choice

Explain the concept of multiple alleles with an example.

• An example of multiple alleles is the color of a person's eyes, which can be blue, green, or brown.

• Multiple alleles refer to the presence of more than two alleles for a particular gene.

• An example of multiple alleles is the ABO blood group system in humans, which has three alleles: A, B, and O.

• An example of multiple alleles is the height of a plant, which can be tall, medium, or short.

Multiple Choice

How do multiple alleles contribute to the variation in traits?

• Multiple alleles only contribute to genetic disorders

• Multiple alleles can result in a wider range of possible phenotypes for a trait.

• Multiple alleles have no impact on trait variation

• Multiple alleles always result in the same phenotype for a trait

Polygenic Inheritance

Several genes influence a characteristic

Genes may be scattered along one chromosome or they can be located on different chromosomes.

Ex: eye color, height, weight, hair and skin
color.

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Multiple Choice

How does polygenic inheritance differ from Mendelian inheritance?

• Polygenic inheritance is not influenced by environmental factors, unlike Mendelian inheritance.

• Polygenic inheritance involves the combined effect of multiple genes on a single trait.

• Polygenic inheritance only occurs in plants, while Mendelian inheritance only occurs in animals.

• Polygenic inheritance involves the effect of a single gene on multiple traits.

Epistasis

Occurs when one gene depends on another gene for it to be expressed.

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• Black labs MUST have at least 1 capital B and 1 capital E in their genotype.

• Brown labs MUST be homozygous recessive for the "b" genotype and have at least 1 capital E.

• Yellow labs can have any "B/b" genotype combination but their "e" genotype MUST be homozygous recessive.

Multiple Choice

Watch the video FIRST and then answer the question.

If both parents are heterozygous for both traits and the offspring ratio is NOT 9:3:3:1, what does that indicate as a type of inheritance?

• Incomplete dominance

• Codominance

• Multiple Alleles

• Polygenic Inheritance

• Epistasis

Multiple Choice

What is epistasis and how does it affect gene expression?

• Epistasis is a genetic interaction where the effect of one gene is dependent on the presence of one or more modifier genes. It can affect gene expression by masking or modifying the effects of other genes.

• Epistasis is a type of protein found in the cell nucleus that regulates gene expression.

• Epistasis is a term used to describe the physical appearance of an organism based on its genetic makeup.

• Epistasis is a process where genes are passed down from one generation to the next.

Characteristics Influenced by Environment

Needs slightly acidic soil

Needs slightly alkaline soil

Multiple Choice

Discuss how environmental factors can influence gene expression.

• Environmental factors can affect gene expression.

• Epigenetic modifications have no connection to environmental factors

• Gene expression is only influenced by internal factors

• Environmental factors have no impact on gene expression

SEX LINKED TRAITS - Sex Determination

XX =

Xy =

female

male

Female karyotype

Male karyotype

Match

Match the sex chromosomes to the corresponding biological gender.

• XX

• XY

• YY

Female

Male

This is not a human example.

• Female

• Male

• This is not a human example.

Who decides?

Mom can only give X
Dad can give X or y

Dads determine sex of babies.

If dad gives X with mom’s X = girl
If dad give y with mom’s X = boy

X

X

X

y

X X

X X

X y

X y

Multiple Choice

Who ultimately determines the gender of the baby?

• Male

• Female

SEX CHROMOSOMES CONTAIN

GENES THAT CODE FOR TRAITS =

SEX LINKED TRAITS

SEX LINKED TRAITS show up
in different % in males and females because they move with the sex chromosomes.

Traits found on the Y chromosome will not be passed on to females.

Traits found on the X chromosomes can be passed to both genders.

Only Males Inherit Y Chromosomes

Y-LINKED GENES:
Genes carried on Y chromosome

EX:
Hairy pinna of the ear

_________genes only show up in _______

Y linked

males.

​(No Hairy Pinna’s for us women!)

Both Males and Females Inherit X Chromosomes: Males XY; Females XX

X-LINKED GENES:

Genes carried on
the X chromosome

EX:

Hemophilia
Colorblindness
Muscular Dystrophy

Around the world, approximately 1 in 12 men and 1 in

200 women are affected by color blindness

When somebody has Protanopia, all shades of green and red
look rather faded, whereas yellow and blue shades seem
largely unaffected. Only around 1% of men experience this
.

People with Tritanopia see colors with a greenish/pink tone. It's
a sporadic form of color blindness and is believed to affect only
0.0001% of men and women .

People with Deuteranomalia see a more subdued color palette,
especially when it comes to colors like green and red. Around
4.63% of men and 0.36% of women experience this type of color
vision deficiency, many of whom don't even realize

Multiple Choice

Who can inherit traits found the Y chromosome?

• Only Males

• Only Females

• Both Males & Females

Multiple Choice

Who can inherit traits found on the X chromosome?

• Only Males

• Only Females

• Both Males & Females

XH

XH

Xh

Make a cross with an X-linked gene

Carrier Mom
Normal Dad

XHXH XHy

XHXh Xh y

GIRLS
_______ = normal
_______ = look normal
but are
CARRIERS

BOYS
_______ = normal
_______ = hemophilia

1
1

1
1

​y

Multiple Choice

Who can be carriers of a trait?

• Males only

• Females only

• Both males and females

Multiple Choice

What does it mean if a female is a carrier?

• They have the recessive trait in their genotype but don't show it phenotypically.

• They have the dominant trait in their genotype but don't show it phenotypically.

• They have the recessive trait in their genotype and do show the trait.

• They have the dominant trait in their genotype and do show the trait.

Multiple Choice

Which of the following is an example of a carrier for a trait?

• XDXD

• XDYd

• XDXd

• XdY

• XDY

Multiple Choice

Discuss the significance of nonmendelian genetics in understanding human traits and diseases.

• Understanding nonmendelian genetics is not important for studying human traits and diseases

• Nonmendelian genetics has no significance in understanding human traits and diseases

• Understanding nonmendelian genetics is crucial for comprehending the complexity of human traits and diseases.

• Nonmendelian genetics only applies to non-human organisms