Quiz 7D

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Quiz 7D

• Variations in Mendel's Theories

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Variations in Mendel's Theories

• Incomplete dominance
• Codominance
• Multiple gene inheritance
• Sex-Linked traits

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Incomplete dominance
a type of inheritance in which the genes
expressing a particular characteristic are
neither dominant or recessive two traits combine
or blend together to produce a different trait (a
blend of two traits) (when offspring of two
homozygous parents show an intermediate phenotype)
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Incomplete dominance
example flower color in snapdragons four
oclock flowers
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Codominance
In codominance the dominant and the recessive
traits are both expressed. Example roan cattle
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Codominance
In incomplete dominance neither allele is fully
dominant. This is different from codominance, in
which both alleles are fully expressed, resulting
in organisms that display the characteristics of
both parents.
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Codominance
In codominance, both alleles are expressed
independently and are uniquely recognizable.
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multiple gene inheritance
multiple gene inheritance (also called Polygenic
Inheritance)- two or more genes producing a
single trait (examples hair color, skin color,
eye color, height, intelligence, body build, etc.)
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How to work incomplete dominance problems.
purebred red X purebred white carnations
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How to work incomplete dominance problems.
Step 1 possible pheotypes and genotypes
Geno
Pheno

• use two different letters to represent genes
• use lower case letters

red white pink
rr ww rw
purebred red X purebred white carnations
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How to work incomplete dominance problems.
r
r
Step 2 parent genotypes
w
w
purebred red X purebred white carnations
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How to work incomplete dominance problems.
r
r
Step 3 fill in possible genotypes of
offspring
w
w
w
r
r
w
w
w
r
r
purebred red X purebred white carnations
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How to work incomplete dominance problems.
r
r
Step 4 Genotipic ratio Phenotipic ratio
w
w
w
r
r
w
w
w
r
r
redwhitepink
rrwwrw
004
purebred red X purebred white carnations