PEDIGREE CHARTS A family history of a genetic

PEDIGREE CHARTS A family history of a genetic condition or trait

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

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

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

Males are represented by the square Females are represented by the circle I II IV

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.

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

SEX LINKED DISORDER: COLOR-BLINDNESS

GENETIC COUNSELORS USE A PEDIGREE CHART TO PREDICT THE PROBABILITY OF TRANSMITTING AN INHERITED DISORDER. Cystic Fibrosis – autosomal recessive

HUNTINGTON’S DISEASE IS AUTOSOMAL DOMINANT.

Genetic Disorders

COMMON GENETIC DISORDERS Syndrome Abnormality Incidence per 10 000 births Lifespan (years) Down Trisomy 21 15 40 Edward's Trisomy 18 3 <1 Patau's Trisomy 13 2 <1 Turner’s Monosomy X 2 (female births) 30 -40 Klinefelter’s XXY 10 (male births) Normal XXX 10 (female births) Normal XYY 10 (male births) Normal

DOWN SYNDROME -Caused by the presence of all or part of an extra 21 st chromosome. -Occurs 1 in every 800 -1000 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.

DOWN SYNDROME. THE ARROW POINTS TO THE EXTRA CHROMOSOME 21.

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.

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.

SICKLE CELL ANEMIA -Defective hemoglobin (only lives 10 -20 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 1000 -1400 Hispanic-Americans

SICKLED CELLS

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