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A family history of a genetic condition or trait
PEDIGREE CHARTS A family history of a genetic condition or trait
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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
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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
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ORGANIZING A PEDIGREE CHART
Generations are identified by Roman numerals & are on different levels. I II III IV
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Males are represented by the square
Females are represented by the circle I II III IV
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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.
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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
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Sex Linked Disorder: Color-Blindness
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Cystic Fibrosis – autosomal recessive
Genetic Counselors use a pedigree chart to predict the probability of transmitting an inherited disorder. Cystic Fibrosis – autosomal recessive
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Huntington’s Disease is autosomal dominant.
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Genetic Disorders
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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
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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.
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The chromosomes of a boy with Down Syndrome
The chromosomes of a boy with Down Syndrome. The arrow points to the extra chromosome 21.
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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.
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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.
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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
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Sickled Cells
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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
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