Download 11-3 Exploring Mendelian Genetics

Introduction To Genetics
Incomplete Dominance,
Codominance, Polygenic Traits &
Multiple Alleles
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Beyond Dominant & Recessive Alleles
Key Concept:
Some Alleles Are
Neither
Dominant Nor Recessive,
Plus Many Traits Are Controlled
By Multiple Alleles or
Multiple Genes.
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Incomplete Dominance
Incomplete Dominance
The Heterozygous Phenotype
Is Between
The Homozygous Phenotypes.
(Both Alleles Expressed In One Cell)
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Codominance
• Both Alleles Completely Expressed
Red Hair Cattle Crossed With White Haired Cattle
Produce
Roan (Pink Brown) Cattle That
Have Both Colored Hairs.
(Both Alleles Expressed Independently.
There are no pink hairs, each hair is either
Red or White.)
(Only One Allele Is Expressed In Each Cell,
BUT Different Cells Express Different Alleles)
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Codominance
RED
WHITE
ROAN
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Multiple Alleles
• A Gene Is Controlled By >2 Alleles.
– Individuals Can Only Have 2 Alleles
– Populations Can Have More Than Two
• Rabbit Fur Color
• Blood Types
• Eye Color
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Human Blood Groups
–ABO
• IA & IB
•i
Codominant
Recessive (Type O gene)
–Rh (Rhesus Monkey)
• Rh+ Dominant
• Rh- Recessive
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Codominance – ABO Blood Type
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Codominance &Multiple Alleles
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Multiple Alleles
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Polygenic Traits
• Phenotypes Produced By The
Interaction Of Several Genes.
– Human Skin Color
Is Controlled By More Than 4 Different
Genes.
– Eye Color
is Controlled By At Least 3 Genes
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Polygenic & Multiple Alleles
Foothill High School Science Department