Download incomplete and co

Incomplete Dominance
Codominance
In a nutshell!
Review: Dominant/Recessive
• One allele is
dominant over the
other (capable of
masking the
recessive allele)
PP = purple
pp = white
Pp = purple
Review Problem:
Dominant/Recessive
• In pea plants, purple flowers (P) are dominant
over white flowers (p) show the cross between
two heterozygous plants.
GENOTYPES:
- PP (1); Pp (2); pp (1)
- ratio 1:2:1
PHENOTYPES:
- purple (3); white (1)
- ratio 3:1
P
p
P
PP
Pp
p
Pp
pp
• Snapdragons
HUH?
http://www.dobermann-review.com/info/genetics/mendels_genetic_laws/Gregor%20Mendel.jpg
http://faculty.pnc.edu/pwilkin/incompdominance.jpg
Incomplete Dominance
R1
F1
X
R2
http://www.google.ca/images?hl=en&q=incoplete%20dominance&rlz=1W1SNNT_enCA397&um=1&ie=UTF-8&source=og&sa=N&tab=wi&biw=1345&bih=555
R2R2 does not produce pigment
F2
Heterozygote only produces ½ pigment of R1R1
http://2.bp.blogspot.com/_uPFMFfHgGGg/SygBEtl5D1I/AAAAAAAAAKc/nylZiiL2k7s/s320/incomplete+dominance.jpg
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.
RR = red
rr = white
Rr = pink
Problem: Incomplete
Dominance
• Show the cross between a pink and a
white flower.
GENOTYPES:
- Rr (2); rr (2)
- ratio 1:1
r
Rr
rr
PHENOTYPES:
- pink (2); white (2)
- ratio 1:1
r
Rr
rr
R
r
Codominance
• The heterozygous condition, both
alleles are expressed equally
• Lots of times, fur color in animals is this
way. (think spotted or 2 colors)
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 don’t blend, but are rather
both present in the offspring.
Roan Horse
http://search.vadlo.com/b/q?rel=2&keys=Dominance+Incomplete+Dominance+Codominance+PPT
Roan Cattle
http://www.ccs.k12.in.us/chsteachers/BYost/Biology%20Notes/CH11notescoincompletedom_files/image004.jpg
Variegated Clover
http://3.bp.blogspot.com/_zUPrgMM5tUg/SSVdrs59_uI/AAAAAAAAAA8/qJGjG2nZPhk/s200/codominance.GIF