GENETICS Traits that are not dominant. Robert Perry MALIBU HIGH SCHOOL
Disclaimer: We have done our best to not infringe on copyrights and other fair-use restrictions. The images in this PowerPoint presentation were downloaded from the world wide web and were considered part of the public domain. In many cases, a web URL is cited for reference. The images are used here for non-profit, non-commercial, educational purposes only. Any image that is NOT available for our non-commercial educational use will gladly be removed immediately by e-mailing our Education Coordinator. Persons using these PowerPoint presentations should not use or redistribute these materials for commercial purposes. bperry@smmusd.org
1
COMPLETE DOMINANCE
2
INCOMPLETE DOMINANCE
3
CODOMINANCE
COMPLETE DOMINANCE PLAIN OLD MENDELIAN DOMINANT AND RECESSIVE ALLELES LIKE WE’VE DONE BEFORE
CARNATIONS
CARNATIONS
RR Rr rr
Rr
The phenotype of the heterozygote gives you the clue.
Rr
RED is completely dominant over WHITE.
Rr
Let’s cross two of these heterozygous (Rr) RED carnations . . .
Rr
Rr = R r R RR R r Rr r Rr rr
R R r
r
R
r
R r 75% RED carnations; 25% WHITE
INCOMPLETE DOMINANCE NOT
SOMETHING NEW: MENDELIAN DOMINANT AND RECESSIVE ALLELES
+ A pure red rose.
A pure white rose.
NEITHER RED OR WHITE ARE DOMINANT ...SO WE END UP WITH PINK
INCOMPLETE DOMINANCE A PINK rose.
RR
Red
Rr
Pink
rr
White
Let’s cross two of these heterozygous (Rr) PINK roses . . .
Rr
Pink
Pink is a “blending” of red and white. Red and white are incompletely dominant
Rr = R r R RR R r Rr r Rr rr
R R r
r
R R r
r
1/4 Red 1/2 Pink 1/4 White
R
r
R r 25% RED roses; 50% PINK; 25% WHITE
CODOMINANCE NOT
SOMETHING NEW: MENDELIAN DOMINANT AND RECESSIVE ALLELES AND NOT INCOMPLETE DOMINANCE.
+ A pure black chicken
A pure white chicken
BLACK & WHITE ARE EQUALLY DOMINANT ...SO WE END UP WITH Erminette
CODOMINANCE An Erminette chicken
BB
Black
Bb
Erminette
bb
White
Let’s cross two of these heterozygous (Bb) Erminette chickens:
Bb
Erminette
Erminette has BOTH black and white. Black and white are CO-DOMINANT
Bb = B b B BB B b Bb b B b bb
B B b
b
B B b
b
1/4 = black 1/2 = Erminette 1/4 = white
B B b
b
25% = black 50%=Erminette 25% = white
Now for some practice problems !