Incomplete Dominance Codominance

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Incomplete DominanceCodominance

• In a nutshell!

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Review Dominant/Recessive

• One allele is dominant over the other (capable of
  masking the recessive allele)

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Review Problem Dominant/Recessive

• In pea plants, purple flowers (P) are dominant
  over white flowers (p) show the cross between two
  heterozygous plants.

P p
GENOTYPES

- PP (1) Pp (2) pp (1) - ratio 121
P p
PHENOTYPES
- purple (3) white (1) - ratio 31
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• Snapdragons

HUH?
http//www.dobermann-review.com/info/genetics/mend
els_genetic_laws/Gregor20Mendel.jpg
http//faculty.pnc.edu/pwilkin/incompdominance.jpg

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Incomplete Dominance
http//www.google.ca/images?hlenqincoplete20do
minancerlz1W1SNNT_enCA397um1ieUTF-8sourceo
gsaNtabwibiw1345bih555
R2R2 does not produce pigment
Heterozygote only produces ½ pigment of R1R1
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http//2.bp.blogspot.com/_uPFMFfHgGGg/SygBEtl5D1I/
AAAAAAAAAKc/nylZiiL2k7s/s320/incompletedominance.
jpg
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Incomplete Dominance

• A third (new) phenotype appears in the
  heterozygous condition.
• Neither trait is completely dominant over the
  other, so a heterozygous plant is a mix.

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Problem Incomplete Dominance

• Show the cross between a pink and a white flower.

GENOTYPES

- Rr (2) rr (2) - ratio 11

PHENOTYPES
- pink (2) white (2) - ratio 11
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Codominance

• The heterozygous condition, both alleles are
  expressed equally
• Lots of times, fur color in animals is this way.
  (think spotted or 2 colors)

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CODOMINANCE

• The condition in which both alleles in a
  heterozygous organism are expressed. (Both are
  dominant together)
• BOTH alleles contribute to the phenotype.
• The two alleles dont blend, but are rather both
  present in the offspring.

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Roan Horse
http//search.vadlo.com/b/q?rel2keysDominanceI
ncompleteDominanceCodominancePPT
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Roan Cattle
http//www.ccs.k12.in.us/chsteachers/BYost/Biology
20Notes/CH11notescoincompletedom_files/image004.j
pg
Variegated Clover
http//3.bp.blogspot.com/_zUPrgMM5tUg/SSVdrs59_uI/
AAAAAAAAAA8/qJGjG2nZPhk/s200/codominance.GIF