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.