Chapter 12 Patterns of Heredity and Human Genetics Section 1 Mendelian Inheritance of Human Traits
Pedigree A pedigree is a graphic representation of genetic inheritance. Symbols are used to show the trait being studied and family relationships
Answer the following about the above pedigree a. What is the sex of I 1? ___________________ b. How many children does IV 2 have? ___________ c. How many children of IV 12 have cancer? ____________ d. List all of the males who have polyps (carriers) __________
Huntingtons Disease Lethal genetic disorder caused by rare autosomal dominant allele Nervous system disintegrates causing loss of control of limbs and mental deterioration.
Huntingtons disease Since onset occurs between ages 30 and 50, this defect can be transmitted to new generations before the parent knows that he is a carrier.
Huntingtons Genetic testing can determine if a person is a carrier. Carriers will get disease because allele is dominant.
Recessive Autosomal Heredity Genetic disorders caused by recessive alleles. Most genetic disorders are caused by this type of allele. Cystic fibrosis, sickle -cell anemia, Tay - Sachs disease, Phenylketonuria (PKU).
Cystic Fibrosis Most common lethal genetic disorder in white Americans. Characterized by thick mucus in lungs and digestive tract. Food is not digested properly Breathing is difficult - frequent lung infections
Tay- Sachs Absence of enzyme that breaks down a lipid that is produced and stored in the central nervous system. Lipid builds up in brain membranes Common in Eastern European Jews and Pennsylvania Dutch.
Symptoms of Tay-Sachs Disease Blindness Progressive loss of movement Mental deterioration Death by age 5. See pg 312 for pedigree
Phenylketonuria (PKU) Most common in people of Norwegian and Swedish descent. Caused by absence of enzyme that converts phenylalanine to tyrosine (amino acids).
Symptoms of PKU New born appears normal. Once baby starts drinking milk, which is high in phenylalanine, damage occurs
Symptoms Build up in phenylalanine causes severe central nervous system damage resulting in mental retardation.
Treatment of PKU All newborns are tested for PKU. Changes in diet can prevent damage.
New Problems With PKU If a homozygous recessive female becomes pregnant, high levels of phenylalanine in her blood can damage baby.