1. Multi-Gene Inheritance

2. Warmup What are the odds of pulling an Ace out of a deck of cards?
What are the odds of pulling a spade?
What are the odds of pulling the Ace of Spades?

3. Multiplication Rule
Odds of two events both happening = odds of one x odds of another

4. Addition Rule
Odds of one of two events happening is odds of one + odds of other
E.g. odds of pulling a heart or diamond = ¼ + ¼ = 1/2

5. Genes on Different Chromosomes
Are inherited independently, due to independent assortment during meiosis

6. Use Multiplication Rule to Solve Crosses of Several Genes
What are the odds two AaBb parents will have an aabb child?
Odds of being aa = ¼, odds of being bb=1/4, odds of being aabb =1/4*1/4 = 1/16

7. On Whiteboard
What are odds AaBbDd dad and aaBbDD mom have a child expressing the dominant phenotype in all 3 genes?

8. Option 2 – If You Don’t Like Multiplication
Make table with all the possible sperm x all the possible eggs
AaBbDD x aaBBDd
ABD
AbD
aBD
abD
ABd

9. On Whiteboard Draw a cross representing AaBbDd x AaBBdd
What are odds of offspring showing dominant phenotype in all 3 traits?
What are the odds of having a child with the identical genotype to one parent?
Double check with multiplication

10. Additional Practice
+ and – represent a secondary blood protein called the Rh factor, with + coding for the protein and – not. + is dominant to -.
What are the odds a man with AB+- and a woman with O- have a child with A+ blood?

11. BUT what about genes on the same chromosome?
Called linked genes
The alleles on a chromosome tend to be inherited together
DRAW out the chromosomes and draw crosses based on that

12. Practice A/a and B/b genes are linked
AABB man mates with an aabb woman. Their children are separated at birth and end up marrying each other and having children. Draw the cross showing the possible genotypes of their grandchildren

13. More Practice
AaBbDd man and AaBbDd woman have lots and lots of children. Half of them show the dominant phenotype in all 3 genes. One quarter of them show the dominant phenotype in A and D only, while the remaining quarter the show the dominant phenotype in B only. Draw the chromosomes of the parents

14. More Challenging Practice
A white-eyed straight winged fly is crossed with a red-eyed curly winged fly. All of the offspring are white-eyed and curly winged. These offspring are then mated with red-eyed straight-winged flies. The resulting F2 generation are half white-eyed curly-winged, one quarter red- eyed curly-winged and one quarter white- eyed straight-winged
Draw the chromosomes for all 3 generations and the crosses that explain the outcome

15. More Complicating Factor
An AaBb fly is crossed with an aabb fly. They produce the following offspring:
Why?
Dominant in Both
Recessive in Both
Dominant in A only
Dominant in B only
% of offspring 45 5

16. Crossing Over
Can be used to figure out the order of genes on a chromosome
The closer 2 genes are on a chromosome, the less likely crossing over occurs between them

17. E.g.
In the case before, the recombination frequency between A and B is 10%
AaCc x aacc
Recombination frequency is 30%
Dominant in Both
Recessive in Both
Dominant in A only
Dominant in B only
% of offspring 45 5
Dominant in Both
Recessive in Both
Dominant in A only
Dominant in C only
% of offspring 35 15

18. On Whiteboard
The recombination frequencies between two genes are shown below for 5 genes on a single chromosome. Order the genes on the chromosome
AB – 15% AC – 5% AD – 40% AE- 10% BC – 20% BD - 25% BE - 5% CD- 45% DE-30%

19. What Would a Recombination Frequency of 50% mean?
AaBb x aabb
Genes are un-linked, or on separate chromosomes
Dominant in Both
Recessive in Both
Dominant in A only
Dominant in B only
% of offspring 25