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Incomplete & Codominance
Biology Honors8.5
Exceptions to Mendel’s Work
Pea plants show complete dominance only
Ex: purple flowers are dominant to white flowers PP=purple Pp=purple pp=white
Sometimes genetics are more complex than that! (actually, they usually are)
Incomplete Dominance
Incomplete Dominance Blending of traits
Neither allele dominates the other Three genotypes = three phenotypes Example: RED flower x WHITE flower PINK
flower
RR = red rr = white Rr = pink
Incomplete Dominance
Make a key to help you!
RR = Red
Rr = Pink
rr = White
Practice, practice, practice!
Oompa Loompa can have red (R), blue (r) or purple hair. Purple hair results from the heterozygous condition. Make a "key" showing the genotypes and phenotypes for hair color.
RR = red rr = blue Rr = purple
Olivia Oompa is married to Odo Oompa and they both have purple hair. What color hair and in what proportion would you expect their children to have?
Codominance
Codominance Both traits are shown
Both alleles are dominant together red x white red & white spotted RR x rr Rr Think “co-” is together (cooperate, coexist)
Codominance Make a key to help
you!RR = RedRr = Roan (red &
white)rr = White
Practice, practice, practice
In a certain species of frogs, purple legs (L) are dominant to black legs (l), but heterozygous genotype results in purple and black legs. Set up a key to show this.
A purple and black legged male mates with a black legged female. What is the chance of having purple legged offspring? Show the cross.