Chapter 12 Patterns of Heredity and Human Genetics

Chapter 12Patterns of Heredity and Human Genetics

I) Mendelian Inheritance of Human Traits • Making a Pedigree • Basics of Pedigrees • How to read & analyze pedigree chart • Symbols:

I) Mendelian Inheritance of Human Traits B) Simple Recessive Heredity • Most genetic disorders are caused by recessive alleles ii) Cystic Fibrosis (CF) • Basics of CF • Common genetic disorder among white Americans • 1/28 Americans -Carriers • 1/2500 White American children have CF

I) Mendelian Inheritance of Human Traits ii) Cystic Fibrosis (CF) • Symptoms & Treatments • CF is caused by a defective protein in the plasma membrane & it causes the formation of a thick mucus in the lungs & digestive tract • Symptoms: in Newborns • Failure to grow • Bulky & greasy stool • Frequent respiratory infections • Symptoms: in children & young adults • Blockage of bowels • Salty taste to skin • Coughing/wheezing • Frequent chest & sinus infections with recurring pneumonia or bronchitis

I) Mendelian Inheritance of Human Traits ii) Cystic Fibrosis (CF) • Symptoms & Treatments • Treatments: • Physical therapy • Special diets • New drugs (anitobiotics, mucus thinning drugs, bronchodilators,etc.)

I) Mendelian Inheritance of Human Traits iii)Tay-Sachs • Basics of Tay-Sachs • Central nervous system disease • What happens? A recessive allele = absence of an enzyme that breaks down a lipid produced & stored in tissues of the central nervous system  lipids not breaking down properly & accumulates in the cells • The recessive allele is common in the U.S. among Ashkenazic Jews from Eastern Europe

I) Mendelian Inheritance of Human Traits iii)Tay-Sachs • Symptoms & treatment • Symptoms: • a relentless deterioration of mental and physical abilities occurs. • Blind • Deaf • unable to swallow • Muscles begin to atrophy and paralysis sets in • Other neurological symptoms (i.e. dementia, seizures, and an increased startle reflex to noise) • Persons with Tay-Sachs also have "cherry-red" spots in their eyes. • Treatments: No Treatment available at this time!!!

I) Mendelian Inheritance of Human Traits iv) Phenylketonuria (PKU) • Recessive disorder due to missing enzyme that converts phenylalanine(Phe)  tyrosine (Tyr) • Most common in U.S. people whose ancestors come from Norway, Sweden or Ireland • How it works? • Babies (homozygous for PKU) born appear normal b/c Mother’s enzyme is working in baby’s system • When PKU babies start to drink milk Phe builds up • Phe accumulates = mental retardation

I) Mendelian Inheritance of Human Traits iv) Phenylketonuria (PKU) • Symptoms & treatments • Symptoms: • Mental retardation • Treatments: • Special diet low in phenylalanine until brains are full developed • Problem: Now that women who are homozygous for PKU can become pregnant they carry high levels of Phenyalanine in their system which can affect the fetus & damage it. What would you do in this situation?

I) Mendelian Inheritance of Human Traits C) Simple Dominant Heredity • Remember the law of dominance- only a single dominant trait is needed in order to express or show the dominant trait ii) Simple Dominant traits • Cleft Chin • Widow’s peak hairline • Free Earlobes • Hitchhiker’s thumb • Almond shaped eyes • Thick lips • Presence of hair on middle section of your fingers

I) Mendelian Inheritance of Human Traits iii) Huntington’s disease (HD) • is a lethal disorder caused by dominant allele (rare) • causes a breakdown of certain areas of the brain • 50% chance of inheriting HD gene from parent w/gene • If no HD gene inherited then no disease

I) Mendelian Inheritance of Human Traits iii) Huntington’s disease (HD) • How it works? • Genetically programmed degeneration of neurons, in certain areas of the brain. This degeneration causes: • uncontrolled movements • loss of intellectual abilities • emotional disturbance

I) Mendelian Inheritance of Human Traits iii) Huntington’s disease (HD) • Symptoms & Treatment • Symptoms: • Onset of the disease – 30-50 years old • b/c of this these individuals can have children pass on the disease before they know they have the disease • Early symptoms of HD: • Mood swings • Depression • Irritability or trouble driving, • Learning new things • remembering a fact, or making a decision. • As the disease progresses, concentration on intellectual tasks becomes increasingly difficult and the patient may have difficulty feeding himself or herself and swallowing

I) Mendelian Inheritance of Human Traits iii) Huntington’s disease (HD) • Treatments-No treatment exists at this point!!! • Genetic tests exist to test to see if you have the dominant allele or not • Why have test? • Helps to make decisions regarding kids • Knowing if you have disease • Potential Test/Quiz question- If you were the government, would you force individuals to get tested if they had the potential for a dominant allele genetic disorder? Why/Why not?

Chapter 12 Patterns of Heredity and Human Genetics