Incomplete Dominance

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Incomplete Dominance Neither allele is dominant over the other Heterozygous offspring have a phenotype that is somewhere between the two.

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Incomplete Dominance. Neither allele is dominant over the other Heterozygous offspring have a phenotype that is somewhere between the two. Incomplete Dominance. Incomplete Dominance. Homozygous red parent: RR crossed with Homozygous white parent: WW RR x WW - PowerPoint PPT Presentation

Transcript of Incomplete Dominance

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Incomplete Dominance

Neither allele is dominant over the otherHeterozygous offspring have a phenotype that is somewhere between the two.

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Incomplete Dominance

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Incomplete Dominance

Homozygous red parent: RRcrossed with

Homozygous white parent: WW

RR x WW yields heterozygous offspring

RW that are pink

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Incomplete Dominance

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Codominance

Both alleles contribute to the phenotype

Heterozygous offspring express both alleles

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Codominance

X

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Codominance: A black chicken crossed with a white chicken results in a speckled chicken

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CODOMINANCE: ABO BLOOD TYPES

Blood type depends on the presence or absence of certain carbohydrates on the surface of red blood cells

3 alleles are possible: IA

IB

i

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ABO BLOOD TYPES

IA and IB are codominant to each other when they are paired.

i allele is recessive to both IA and IB

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ABO Blood Groups

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ABO Blood Groups

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ABO Blood Types

Blood typing is actually far more complicated than “A”, “B”, and “O”

ABO are the MAJOR antigens There are also MINOR antigens

Rh factor: “+” or “-”

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ABO Blood Types

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ABO Blood Types

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ABO Blood Types

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ABO Blood Types

Why is it important to get the right blood type when getting a transfusion? Transfusion Reactions

Immune system (antibodies) will attack cells that have an antigen that the body doesn’t recognize as “self”

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Transfusion Reaction

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Multiple Alleles

More than 2 possible alleles exist in a population

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Multiple AllelesCoat color in rabbits: there are at least 4

different alleles C = full color (dominant to all other

alleles) c (ch) = chinchilla c (h) = himalayan c = albino (recessive to all other alleles)

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Full color rabbit

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Chinchilla rabbit: partial defect in pigmentation

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Himalayan rabbit: color in only certain parts of body

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Albino rabbit: no color; recessive to all other alleles

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Polygenic Traits

Traits that are produced by the interaction of more than one different genes

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Polygenic Inheritance

For example: coat color in Labrador retrievers is a result of interaction of 2 different genes.

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Polygenic Inheritance

Example: comb shape in chickens is a result of interaction between 2 different genes.

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X-Linked Inheritance

Early 1900’s Thomas Morgan’s fruit fly studies

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X-Linked Inheritance

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X-Linked Inheritance More than 300 human traits are X-

linked. Most common X-linked recessive

disorders: Hemophilia Red-green colorblindness Duchenne muscular dystrophy Adrenoleukodystrophy (seen in the

movie Lorenzo’s Oil)

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BARR BODIES

Barr body is found only in females It is a darkly staining area in the

nucleus of a cell that represents an inactivated X chromosome

One X chromosome is randomly inactivated

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Barr Body

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Barr Body

Do you see the Barr body?

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Barr Body: X inactivation

Calico cat Generally all females Have one X chromosome coding for for

gold color, and one X chromosome coding for black color

Color pattern shows how one X chromosome in each cell is randomly inactivated

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Calico Cat

There have been instances of male Calico cats found How could this happen?

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Male Calico cat?

HINT: Male calico cats are sterile

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Male Calico cat?

Answer: Male Calico cats have XXY chromosome configuration A Klinefelter’s cat? Yup, it happens.