1. A family history of a genetic condition or trait
PEDIGREE CHARTS
A family history of a genetic condition or trait

2. What is a pedigree chart?
Pedigree charts show a record of the family of an individual.
They can be used to study a hereditary condition or trait.
They are especially useful when there are large families that cover several generations.
© 2007 Paul Billiet ODWS

3. Studying human genetics
Today genetic engineering has new tools to offer doctors studying genetic diseases
A genetic counselor will still use pedigree charts to help determine the distribution of a disease in an affected family
© 2007 Paul Billiet ODWS

4. ORGANIZING A PEDIGREE CHART
Generations are identified by Roman numerals & are on different levels. I II
III IV

5. Males are represented by the square
Females are represented by the circle I II
III IV

6. Parents are connected with a horizontal line.
Offspring are below the parents and the bracket is connected by a vertical line.
Siblings are within the same bracket.

7. READING THE SYMBOLS USED IN PEDIGREE CHARTS
A marriage with five children, two daughters and three sons. The eldest son is affected by the condition.
Eldest child  Youngest child
Normal male
Affected male
Normal female
Affected female
Marriage
© 2007 Paul Billiet ODWS

8. Sex Linked Disorder: Color-Blindness

9. Cystic Fibrosis – autosomal recessive
Genetic Counselors use a pedigree chart to predict the probability of transmitting an inherited disorder.
Cystic Fibrosis – autosomal recessive

10. Huntington’s Disease is autosomal dominant.

11. Genetic Disorders

12. Common Genetic Disorders
Syndrome
Abnormality
Incidence per births
Lifespan (years)
Down
Trisomy 21 15 40
Edward's
Trisomy 18 3
<1
Patau's
Trisomy 13 2
Turner’s
Monosomy X
2 (female births)
30-40
Klinefelter’s
XXY
10 (male births)
Normal
XXX
10 (female births)
XYY

13. Down Syndrome
-Caused by the presence of all or part of an extra 21st chromosome.
-Occurs 1 in every births.
-Risk having a baby with Down Syndrome increases as the mother’s age increases.
-Can be determined before birth (amniocentesis or umbilical blood sampling).
-Down Syndrome is usually not inherited.

14. The chromosomes of a boy with Down Syndrome
The chromosomes of a boy with Down Syndrome. The arrow points to the extra chromosome 21.

15. Characteristics -Short stature.
-Flat broad face with small ears and nose.
-Upward slanting eyes.
-Small mouth with short roof.
-Hypertonia (floppy muscles).
-Heart defects are common.
-Often are mild mentally delayed.

17. Edward’s (Trisomy 18) -Most common trisomy after Down’s.
-Occurs at the meiotic divisions.
-Most fetus’ die in utero.
-Only 5-10% survive the first year of life. Some survive to adulthood!
-Cause of death-apnea and heart abnormalities.
-Many visible malformations.

19. Sickle Cell Anemia
-Defective hemoglobin (only lives days vs 120 days)
-Symptoms: constant and/or severe pain, shortness of breathe, jaundice, delayed growth
-Health issues: infections, strokes, acute chest syndrome
-Most affected: 1 in 500 African-Americans, 1 in Hispanic-Americans

20. Sickled Cells

21. Hemophilia A disorder in which blood doesn't clot normally. Symptoms:
-many large or deep bruises
-joint pain and swelling
-unexplained bleeding
-blood in urine or stool