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

2. What is a Pedigree Chart?
Slide # 2
1. Pedigree chart traces the inheritance of a particular trait through several generations.
2. One GOAL of using a pedigree chart is to determine carriers and the likelihood that future generations could be affected.
Carrier: someone who carries the gene but is unaffected by the genetic disorder. The person must be heterozygous and the trait recessive.

3. Constructing a Pedigree
Slide # 3
Constructing a Pedigree
Female .
Male

4. Constructing a Pedigree
Slide # 4
Constructing a Pedigree
1. Couple:
Horizontal Line
2. Children:
- Vertical line
3. More than one child:
a horizontal line is drawn with a vertical line coming down for each child, in order of birth from left to right.

5. Constructing a Pedigree
Slide # 5
1. Fraternal twins- (same or different gender)
a. Two line branching from the same point
b. Two different eggs and two different sperm cells.
2. Identical twins (same gender)
Similar to fraternal twins with an additional horizontal line.
One egg and one sperm unite and later splits to create two babies

6. Generations 1. Roman numerals indicate generations.
Slide # 6
1. Roman numerals indicate generations.
2. Birth Order: children are listed in birth order with oldest on left and youngest on the right. I II
III

7. More Symbols in a Pedigree Chart
Slide # 7
More Symbols in a Pedigree Chart
Full Shaded:
Affected with the disorder
2. Half shaded:
Carrier (recessive)
3. Deceased

8. Predicting using Pedigree Charts
Slide # 8
1. Pedigrees are used to find out:
a. who are carriers of the disorder
b. the probability of having a future child with the disorder.
2. To begin to interpret a pedigree, first determine if the disorder is:
a. Autosomal dominant
b. Autosomal recessive
c. Sex-linked (carried on the X chromosome)

9. Interpreting a Pedigree Chart
Slide # 9
First ask:
Is it a Sex-linked or Autosomal Disorder?
1. If there is a much larger number of males than females who are affected then the disorder is probably Sex-linked.
2. If there is a 50/50 ratio between males and females who are affected then the disorder is likely autosomal.

10. Interpreting a Pedigree Chart
Slide # 10
If it is autosomal disorder then ask:
Is it dominant or recessive?
Does the trait skip a generation anywhere on the pedigree? If so, recessive. If not, the trait MAY be recessive.
If two parents do not show the trait and their children do show it, then it is an autosomal recessive disorder(parents are carriers or heterozygous)
If the disorder is autosomal dominant, then at least one of the parents must show the disorder.

11. Note: The following pedigree charts show affected individuals only.
Slide # 11
The following pedigree charts show affected individuals only.
Carriers are unknown at this point.

12. Practice Examples Sex-linked or Autosomal disorder? Answer:
Slide # 12
Does this pedigree show a
Sex-linked or Autosomal disorder?
Answer:
Sex-Linked disorder
much larger number of males are affected

13. Practice Examples Sex-linked or Autosomal disorder? Answer:
Slide # 13
Does this pedigree show a
Sex-linked or Autosomal disorder?
Answer:
Autosomal disorder 50/50 ratio between males and females

14. Does this pedigree show a Autosomal Dominant or Recessive disorder?
Practice Examples
Slide # 14
Does this pedigree show a Autosomal Dominant or Recessive disorder?
Answer:
Autosomal dominant disorder
At least one parent of the affected children show the disorder

15. Practice Examples Sex-linked or Autosomal disorder? Answer:
Slide # 15
Does this pedigree show a
Sex-linked or Autosomal disorder?
Answer:
Autosomal disorder 50/50 ratio between males and females

16. Does this pedigree show a Autosomal Dominant or Recessive disorder?
Practice Examples
Slide # 16
Does this pedigree show a Autosomal Dominant or Recessive disorder?
Answer:
Autosomal recessive disorder
Two parents do not show the trait but their children do show it (heterozygous parents)

17. Now Draw… Sketch the next pedigree onto your notebook.
Write the genotypes below the individuals.
Individuals affected will be dd.
Color in carriers (color half of the shape)
Title with the appropriate words…
Autosomal vs . Sex-linked
Dominant vs Recessive

18. DON’T SCROLL AHEAD UNTIL YOU’VE TRIED THE PEDIGREE!!!
WHAT IS D?

19. Genotypes and Carrier determination D = Normal hearing d = deafness
Autosomal Recessive
Genotypes and Carrier determination
D = Normal hearing d = deafness
Slide # 17 Dd Dd dd Dd D? Dd