1. Non-Mendelian Genetics

2. Mendelian Genetics: Dominant & Recessive Review
One allele is DOMINANT over the other (because the dominant allele can “mask” the recessive allele)
genotype: PP
genotype: pp
genotype: Pp
phenotype: purple
phenotype: white
phenotype: purple

3. 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 (25%) Pp (50%)
pp (25%)
- ratio 1:2:1 P p PP Pp Pp pp
PHENOTYPES:
- purple (75%) white (25%)
- ratio 3:1

4. Non-Mendelian Genetics
Incomplete Dominance
Codominance
Multiple Alleles
Polygenic Traits
Sex-Linked Traits

5. Incomplete Dominance
a third (new) phenotype appears in the heterozygous condition as a BLEND of the dominant and recessive phenotypes. Ex - Dominant Red (R) + Recessive White (r) = Hybrid Pink (Rr)
RR = red
rr = white
Rr = pink

6. Problem: Incomplete Dominance
Show the cross between a pink and a white flower.
GENOTYPES:
R r
- RR (0%) Rr (50%) rr (50%)
- ratio 1:1 r Rr rr Rr rr
PHENOTYPES:
- pink (50%); white (50%)
- ratio 1:1

7. Codominance NS = some of each NN = normal cells SS = sickle cells sick
in the heterozygous condition, both alleles are expressed equally with NO blending! Represented by using two DIFFERENT capital letters.
Example: Dominant Black (B) + Dominant White (W) = Speckled Black and White Phenotype (BW)
Sickle Cell Anemia -
NS = some of each
NN = normal cells
SS = sickle cells
sick

8. Codominance Example: Speckled Chickens
BB = black feathers
WW = white feathers
BW = black & white speckled feathers
Notice –
NO GRAY!
NO BLEND!
Each feather is
either black or white

9. Codominance Example: Rhodedendron
R = allele for red flowers
W = allele for white flowers
Cross a homozygous red flower with a homozygous white flower.

10. Codominance Example: Roan cattle
cattle can be red (RR – all red hairs) white (WW – all white hairs) roan (RW – red and white hairs together)

11. Codominance Example: Appaloosa horses
Gray horses (GG) are codominant to white horses (WW). The heterozygous horse (GW) is an Appaloosa (a white horse with gray spots).
Cross a white horse with an appaloosa horse.
W W G W GW GW WW WW

12. Problem: Codominance
Show the cross between an individual with sickle-cell anemia and another who is a carrier but not sick.
N S
GENOTYPES:
- NS (50%) SS (50%)
- ratio 1:1 S NS SS
PHENOTYPES:
- carrier (50%) sick (50%)
- ratio 1:1

13. Multiple Alleles
there are more than two alleles for a gene. Ex – blood type consists of two dominant and one recessive allele
options. Allele A
and B are
dominant over
Allele O (i)

14. Multiple Alleles: Lab Mouse Fur Colors
Fur colors (determined by 4 alleles): black agouti yellow

15. Multiple Alleles: Rabbit Fur Colors
Fur colors (determined by 4 alleles): full, chinchilla, himalayan, albino

16. Multiple Alleles: Blood Types (A, B, AB, O)
Rules for Blood Types:
A and B are co-dominant (Both show)
AA or IAIA = type A
BB or IBIB = type B
AB or IAIB = type AB
A and B are dominant over O (Regular dom/rec)
AO or IAi = type A
BO or IBi = type B
OO or ii = type O

17. Multiple Alleles: Blood Types (A, B, AB, O)

18. Allele (antigen) on RBC surface
Phenotype
Possible Genotype(s)
Allele (antigen) on RBC surface
Can Donate Blood To
Can Receive Blood From A
IAi
IAIA
A, AB
A, O B
IBi
IBIB
B, AB
B, O AB
IAIB
A, B, AB, O O ii

19. Problem: Multiple Alleles
Show the cross between a mother who has type O blood and a father who has type AB blood.
GENOTYPES:
i i
- Ai (50%) Bi (50%)
- ratio 1:1 A B Ai Bi
PHENOTYPES:
- type A (50%) type B (50%)
- ratio 1:1

20. Problem: Multiple Alleles
Show the cross between a mother who is heterozygous for type B blood and a father who is heterozygous for type A blood.
GENOTYPES:
A i
AB (25%); Bi (25%);
Ai (25%); ii (25%)
- ratio 1:1:1:1 B i AB ii Bi Ai
PHENOTYPES:
type AB (25%); type B (25%)
type A (25%); type O (25%)
- ratio 1:1:1:1

21. Polygenic Traits
traits produced by multiple genes
example: skin color

22. Sex-Linked Traits
Gene is attached to the X chromosome only, not found on the Y chromosome at all. (women have XX, men have XY chromosomes). These disorders are more common in boys.
examples: red-green colorblindness

23. Sex-Linked Traits
in males, there is no second X chromosome to “mask” a recessive gene. If they get an X with the disorder, they have it. Girls must inherit defective X’s from both parents.

25. Sex-Linked Traits A: 29, B: 45, C: --, D: 26  Normal vision
 Red-green color blind
A: 70, B: --, C: 5, D: 6
 Red color blind
A: 70, B: --, C: 5, D: 2
 Green color blind