1. Pedigree Charts
Day 103

2. DN 103 T/F Every chromosome is different between a man and a woman
T/F Men and women have different numbers of chromosomes in their sex cells
T/F If you looked in a cell during mitosis and you could see the chromosomes lining up, you could tell whether the cell belonged to a man or a woman

3. Review
Male
Meiosis
Sex Cell
Mitosis
Sex Cell
Meiosis
Female

4. In lions, (A) is the allele for dark eyes and (a) is the allele for light eyes.
Male Aa
Sex Cell (A)
Meiosis
Sex Cell (a)
Sex Cell (A)
Meiosis
Sex Cell (a)
Female Aa

5. Human Chromosomes

6. Sex-Linked Disorders
How would a person inherit a sex-linked disorder?

7. Sex-Linked Disorders
Y chromosome does not carry all of the genes of an X chromosome
Females have two X chromosomes, so they carry two copies of each gene found on the X – backup!
Genes for certain disorders are carried on X chromosome

8. Sex-Linked Disorders
Because the gene for these is recessive, and men only have 1 X chromosome, men are more likely to have sex-linked disorders (if they have the gene, they will express it – diseases like this are called HEMIZYGOUS)
Women need two copies of the gene to express it
Men only need ONE
Colorblindness – inability to distinguish between red/green
Hemophilia - Prevents blood from clotting – even small cuts can be fatal

9. Let’s make a pedigree chart!

10. Pedigree Charts Women are represented by circles
Men are represented by squares/rectangles

11. Pedigree Charts
When they get married…

12. Pedigree Charts
When they have babies…

13. Pedigree Charts How many daughters did they have?
How many sons did they have?
Was their oldest child a son or a daughter?

14. Pedigree Charts
What happens when the children get married?

15. Let’s PRACTICE on the Briggs Family
Alicia married Drew…

16. Briggs Family
And they have three children, Chelsea, John and Daniel

17. Briggs Family
Daniel marries a lovely girl named Anna…

18. Briggs Family
… and they have two daughters, Jocelyn and Stephanie…

19. Briggs Family
Stephanie marries a man who loves and respects her, named Jeff…

20. Briggs Family
… and they have three children, Nick, Caroline and Michael

21. Disaster strikes the Briggs Family
OOOOOHHH NOOOOOOOO!
Alicia and Drew were both carriers of a recessive disease…

22. Briggs Family
Chelsea has the disease, Daniel is a carrier…

23. Briggs Family Whew! Anna is not a carrier!
Can Daniel and Anna pass the disease on to their children?

24. Briggs Family
Ruh roh… Stephanie and Jocelyn both carry the disease.

25. Briggs Family
Bad luck… Jeff is a carrier…

26. Briggs Family DISASTER
Nick and Caroline both suffer from the disease.
Assuming Michael gets married to someone who doesn’t have the disease, and is not a carrier, can his children get the disease?

27. Recessive vs. Sex-Linked
What is the difference between recessive traits and sex-linked traits?
How does this change the pedigree chart?

28. Recessive vs. Sex-Linked
If a trait is carried on the X chromosome, women are carriers. They have a back-up X chromosome in case of a mutation.
Remember:
Women need two copies of the gene to express it
Men only need ONE
Men…
Do NOT have a back up X chromosome
If Mom is carrying the gene, men have a chance of suffering from the disease!

30. ES 103
Draw a pedigree chart (different from the one we did in class), showing family members that passed down a disease through three or more generations.