1. Non-Mendelian Problems

2. I Sex-linked Traits
These are Traits (genes) that are located on the sex chromosomes.
Sex chromosomes are X and Y
XX genotype for females
XY genotype for males
Many sex-linked traits are carried on X chromosome of the sex chromosomes
That is why these genetic disorders are found mainly in males, there is no gene for this trait on the Y chromosome to cancel out a bad gene on the X chromosome

3. Sex-linked Traits Example: Eye color in fruit flies Sex Chromosomes
XX chromosome - female
Xy chromosome – male
-the trait will be determined
by the gene on the X, none
On the Y
fruit fly
eye color

4. Sex-linked Trait Problem
Use the same principles used in the Mendelian Monohybrid problems, except that the sex of the offspring must be included and the Y chromosome will not have an allele
Example: Eye color in fruit flies
(red-eyed male) x (white-eyed female) XRY x XrXr
Remember: the Y chromosome in males does not carry traits.
RR = red eyed
Rr = red eyed
rr = white eyed
XY = male
XX = female XR Xr Y

5. XRXR—FEMALE w/ HOMOZYGOUS DOM XRXr—FEMALE w/ HETERZYGOUS
POSSIBLE GENOTYPES IN SEX-LINKED PROBLEMS:
XRXR—FEMALE w/ HOMOZYGOUS DOM
XRXr—FEMALE w/ HETERZYGOUS
XrXr—FEMALE w/ HOMOZYGOUS REC
XRY—MALE w/ DOM ALLELE
XrY—MALE w/ REC ALLELE

6. Sex-linked Trait Solution:
Genotypic Ratio:
50% XR Xr
50% Xr Y
Phenotypic Ratio:
50 % white eyed male
50 % red eyed female XR Xr Y
XR Xr
Xr Y

7. Sex-linked Cross ?s from previous problem
1. What % of the males will be red eyed?
2. What % of the offspring will be red eyed?
3. What % of the offspring will be males?
4. What % of the females will be white eyed?
5. What % of the females will be red eyed?
6. What % of the offspring will be white eyed?

8. Female Carriers
*1/2 filled in box=carrier, filled in box=affected individual

9. Incomplete Dominance

10. Incomplete Dominance
F1 hybrids have an appearance somewhat in between the phenotypes of the two parental varieties. There is a mixing of the two traits, neither is dominant over the other. Worked like Monohybrid problems except that you will use all capitals letter for each trait, ex. Red=RR, white=WW Pink=RW
Ex: snapdragons (flower)
red (RR) x white (WW)
RW=pink flower
RR = red flower
WW = white flower W
*Fill in the square to the left R

11. Incomplete Dominance R W W Genotypic Ratio: 0:4:0—100%RW
Phenotypic Ratio:
0:4:0—100%pink
produces the
F1 generation RW

12. Incomplete Dominance Problem:
In cattle when a red bull(RR) is mated with white(WW) cow the offspring are roan(RW) a blending of red and white. Mate a red bull with a roan cow. Use the format on the next slide and give the P1, do the Punnett Square, and give the genotypic and phenotypic ratios for F1 generation of this cross.

13. P1 = __RR__ x __RW__ Genotypic ratio: ____ : _____ : _____
Phenotypic ratio: ____ : _____ : _____

14. P1 = __RR__ x __RW__ R W R RR RW RW R RR 2 2 2 2 or 50%RR,50%RW
or 50%RR,50%RW
Genotypic ratio: ____ : _____ : _____ 2 2
or 50%RED,50%ROAN
Phenotypic ratio: ____ : _____ : _____

15. Incomplete Dominance

16. Dihybrid Cross
A breeding experiment that tracks the inheritance of two traits.
Mendel’s “Law of Independent Assortment”
a. Each pair of alleles segregates independently during gamete formation
b. Formula: 2n (n = # of heterozygotes)

17. Question: How many gametes will be produced for the following allele arrangements?
Remember: 2n (n = # of heterozygotes)
1. RrYy
2. AaBbCCDd
3. MmNnOoPPQQRrssTtQq

18. Answer: 1. RrYy: 2n = 22 = 4 gametes RY Ry rY ry
2. AaBbCCDd: 2n = 23 = 8 gametes
ABCD ABCd AbCD AbCd
aBCD aBCd abCD abCD
3. MmNnOoPPQQRrssTtQq: 2n = 26 = 64 gametes

19. All possible gamete combinations by FOIL method
Dihybrid Cross
Traits: Seed shape & Seed color
Alleles: R round r wrinkled Y yellow y green
RrYy x RrYy
RY Ry rY ry
RY Ry rY ry
All possible gamete combinations by FOIL method

20. Dihybrid Cross RY Ry rY ry RY Ry rY ry

21. Dihybrid Cross RY Ry rY ry Round/Yellow: 9 Round/green: 3
wrinkled/Yellow: 3
wrinkled/green: 1
9:3:3:1 phenotypic ratio
RRYY
RRYy
RrYY
RrYy
RRyy
Rryy
rrYY
rrYy
rryy

22. Dihybrid Cross
Round/Yellow: 9 Round/green: 3 wrinkled/Yellow: 3 wrinkled/green: 1
9:3:3:1

23. CODOMINANCE

24. Multiple Alleles /Codominance
Non-Mendelian Cross where 2 alleles are expressed (multiple alleles) in heterozygous individuals.
Example: blood type
Use the genotypes below whenever doing blood type crosses.
1. type A = AA -pure or AO -hybrid
2. type B = BB -pure or BO -hybrid
3. type AB = AB -codominant
4. type O = OO -pure

25. Codominance Problem
Example: Cross a male who is homozygous Type B (BB) x a female that is heterozygous Type A (AO)
Genotypic ratio:
50% IAIB
50%= IBi IB IA i
IAIB
IBi
Phenotypic ratio:
50% type AB
50%= type B

26. Another Codominance Problem
Example: Cross a
male Type O (ii) x female type AB (IAIB) i IA IB
*Give the genotypic and phenotypic ratios of the offspring

27. Another Codominance Problem
Example: male Type O (ii) x female type AB (IAIB) i IA IB
Genotypic Ratio:
50% IAi
50% IBi
IAi
IBi
Phenotypic Ratio:
50% type A
50% type B

28. Codominance
Question: If a boy has a blood type O and his sister has blood type AB, What are the genotypes and phenotypes of their parents?
boy - type O (ii) X girl - type AB (IAIB)

29. Codominance Answer: IB IA i IAIB ii Parents: genotypes = IAi and IBi
phenotypes = A and B