1. Pedigree Charts The family tree of genetics What is a pedigree? What is a pedigree? Constructing a pedigree Constructing a pedigree Interpreting a pedigree Interpreting a pedigree

2. Some History  Hemophilia has played an important role in Europe's history  The disease began to crop up in Great Britain's Queen Victoria’s children  It became known as the "Royal disease" because it spread to the royal families of Europe through Victoria's descendants

3. How it Spread  it spread through the Royal Houses of Europe as monarchs arranged marriages to consolidate political alliances.  We can trace the appearance of hemophilia as it popped up in Spain, Russia, and Prussia by looking at the family tree.

4. The Royal Family Tree

5. What is a Pedigree Chart?  A Pedigree chart traces the inheritance of a particular trait through several generations.  One GOAL of using a pedigree chart is to figure out who are carriers of the trait, because this information is typically unknown.

6. Steps to Creating a Pedigree 1.A genetic counselor will first gather information regarding who the family members are and how are they related. This will go back a few generations. 2.The genetic counselor will then ask who has the trait of interest. (Shows the trait) 3.After researching, the genetic counselor uses all of this information to construct a Pedigree chart, with all the family members’ names and genotypes written below each symbol.

7. Constructing a Pedigree  Male  Female

8.  Married Couple- –Horizontal Line  Siblings –Vertical line  More than one Sibling: –a horizontal line is drawn with a vertical line coming down for each sibling. Constructing a Pedigree

9. I II III Constructing a Pedigree Roman numerals to the left of the pedigree show the generations. Birth Order: children are listed in birth order with oldest on left and youngest on the right.

10.  Fraternal twins- –Two line branching from the same point –two eggs and two sperm cells.  Identical twins- –Also called Maternal Twins –Identical or Maternal Twins (first set above) are drawn branching off of the same point, but are also connected to each other Constructing a Pedigree

11. More Symbols in a Pedigree Chart  Full Shaded: –Affected person who shows a disorder  Half shaded: –Autosomal carrier  Circle with dot: –X-linked carrier –always female  Deceased

12. Sex-Linked Traits  Genes located on the X chromosomes (some cause diseases)  The Y is much smaller, contains few genes  Sex Linked Disorders –Color Blindness (red-green) –Hemophilia ("bleeders disease) –Duchenne Muscular Dystrophy (weakening/loss of skeletal muscles)  More common for males to display disorders

13. Sex-Linked Traits  Consider hemophilia

14. How do you find the genotypes of the persons in the chart?  Start with the person showing the trait.  Look at parents of this individual and ask yourself: what would the parent’s genotypes have to be (in a Punnett square) to produce an offspring with this genotype?  If there is not enough information to figure out the entire genotype then a question mark is used to take the place of the uncertain allele. Ex. T?

15.  Is deafness a dominant or recessive trait?  To show deafness, what genotype does this son have to have?  For two parents who have normal hearing to have a deaf son, they both must be carrier. What are the parent genotypes? Example Problem Shaded=deaf (D) is normal hearing (d) is deaf recessive dd Dd

16.  Write the genotypes for the parents and son under the correct circle/boxes, half-shading carriers. Example Problem Shaded=deaf (D) is normal hearing (d) is deaf Dd dd

17.  Pedigrees are used to find out: –who are carriers of the disorder & –the probability of having a future child with the disorder.  To begin to interpret a pedigree, first determine if the disorder is: –Autosomal dominant –Autosomal recessive –Sex-linked (carried on the X chromosome) Predicting using Pedigree Charts

18. Interpreting a Pedigree Chart First ask: Is it a Sex-linked or Autosomal Disorder? –If there is a much larger number of males than females who are affected then the disorder is Sex-linked. –If there is a 50/50 ratio between males and females who are affected then the disorder is autosomal.

19. Interpreting a Pedigree Chart If it is autosomal disorder then ask: Is it dominant or recessive? –If two parents do not show the trait and their children do show it, then it is an autosomal recessive disorder  (parents are heterozygous) –If the disorder is autosomal dominant, then at least one of the parents must show the disorder.

20. Note:  The following pedigree charts show infected individuals only.  Carriers are unknown at this point.

21. Practice Examples Does this pedigree show a Does this pedigree show a Sex-linked or Autosomal disorder?

22. Answer: Sex-Linked Disorder much larger number of males are affected

23. Practice Examples Does this pedigree show a Does this pedigree show a Sex-linked or Autosomal disorder?

24. Answer: Autosomal Disorder 50/50 ratio between males and females

25. Practice Examples Does this pedigree show a Autosomal Dominant or Recessive disorder? Does this pedigree show a Autosomal Dominant or Recessive disorder?

26. Answer: Autosomal Dominant Disorder At least one parent of the affected children show the disorder

27. Practice Examples Does this pedigree show a Does this pedigree show a Sex-linked or Autosomal disorder?

28. Answer: Autosomal Disorder 50/50 ratio between males and females

29. Practice Examples Does this pedigree show a Autosomal Dominant or Recessive disorder? Does this pedigree show a Autosomal Dominant or Recessive disorder?

30. Answer: Autosomal Recessive Disorder Two parents do not show the trait and their children do show it (heterozygous parents)

31. dd Dd Autosomal Recessive Genotypes and Carrier determination D = Normal hearing d = deafness Dd D?