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  1. Dominant Trait
    One gene is able to express itself regardless of the presence of the other gene
  2. Recessive Traits
    • Parents of individual may have not have the trait
    • Tends to skip a generation
    • Rare
    • May see consanguinity (blood relatives
    • mating)
  3. Recessive Trait
    • It is possible that:
    • Neither parent has the characteristic of child, but both parents are carriers of one recessive faulty gene
    • Or one or both parents have two faulty genes and all offspring have disease
  4. Genotype
    the genes of the individual
  5. Phenotype
    the physical appearance of the individual
  6. Carrier of a Recessive Trait
    • An individual who has a recessive gene but is unaffected.
    • They have the genotype, but not the phenotype
    • They are able to pass the trait to their offspring
  7. Genetic disorders of interest
    Autosomal = non-sex chromosome
    • Autosomal Recessive Disorders:
    • Tay-Sachs disease: lack of the enzyme
    • Cystic fibrosis: abnormal protein in cell membrane
    • Phenylketonuria (PKU): lack of an enzyme
    • Sickle-Cell disease: Abnormal RBCs
    • Autosomal Dominant Disorders:
    • Marfans Syndrome: defect in elastic connective tissue;
    • Huntington disease: too many amino acids
  8. Recessive: Tay Sachs Disease
    • Tay Sachs Disease – missing or decreased amounts of an important enzyme (Hex A) –
    • Absence of Hex A allows lipids to build up in lysosomes of cells.
  9. Tay Sachs Disease
    • More common in Jewish populations
    • Lipids accumulate in brain cells
    • Child’s development slows around 4-8 months old
    • Progressive neurological problems
    • Blind, seizures, paralyzed, death
  10. Recessive Disease
    Cystic Fibrosis - Genetic disease causing lung and digestive problems
  11. Cystic Fibrosis (CF) and Heredity
    • Body produces thick, sticky mucus that clogs the lungs, leads to infection, and serious digestive disorders
    • Most common, fatal genetic disease in US
    • Mutations in a single gene, (CFTR) gene, causes CF
  12. Fibrosis
    • More common in Caucasians
    • Chloride ions can’t pass thru cell membrane
    • Build up of thick mucus in lungs and pancreas
    • Digestive and breathing problems
  13. PKU (recessive)
    • Phenylketonuria (PKU) – lacks the enzyme to metabolize phenyalanine (protein levels increased in blood and urine)
    • Normal development if placed on low phenylalanine diet (especially while brain is developing)
    • Build up of phenylalanine affects nervous system
  14. PKU
    • Newborns routinely tested for phenylalanine level in blood
    • Treatment is diet low in phenylalanine
  15. Sickle Cell Disease and Heredity
    • RBC are irregularly shaped
    • Caused by a mutation in the hemoglobin-Beta gene found on chromosome 11
    • Most common inherited blood disorder in the United States
  16. Sickle Cell
    • Because of irregular shape, blood cells get trapped in small blood vessels
    • Disease causes great pain (“crisis”) and increased risk of infections and blockage of vessels
  17. Test for Sickle Cell
    • Blood test that checks for hemoglobin S, the defective form of hemoglobin
    • Can also be detected in an unborn baby via amniocentesis
    • Diagnosis is confirmed by visualizing “sickled” cells on a blood sample
  18. Testing for Genetic Disorders:
    • Testing for a protein
    • •Tay-Sachs—lack the enzyme hex A.
    • •PKU—a lot of phenylalanine in the blood.
    • Testing the DNA
    • •Use of a genetic marker to test for a genetic mutation.
    • •Use of a DNA chip to test for mutated genes.
  19. Dominant Traits
    • Males and females equally affected
    • Affected individuals have one affected parent
    • Characteristics may be present in all generations
  20. Huntington Disease
    • Dominant
    • Progressive degeneration of brain cells
    • Mutated gene for protein (huntington)
    • Often did not know had disease until middle age – already had kids and passed it to them.
    • Death occurs 10-15 yrs after onset
    • Now know defect is on chromosome 4 and can test for it
  21. Genomics
    • --the study of our genes and the genes of other organisms.
    • •The goal/purpose is to:
    • –Learn about abnormal
    • sequences that lead to illnesses. Develop drugs to combat these illnesses.
    • –Learn about proteomics—knowledge of the structure and
    • function of proteins in the cell.
    • –Bioinformatics—the application of computer technologies to the study of the genome.
    • Look at patterns &Multifactorial genes
  22. Human Genome Project (HGP)
    • Genes are the code for proteins that make up all of our traits (A,T,C,G)
    • We have 20-25,000 genes!
    • HGP was a 13 year project completed in 2003 to identify all our genes
  23. Genetic Testing
    • Positive outcomes
    • –Diagnosing and predicting disease or susceptibility
    • –Disease intervention (designing drugs to target specific sites in body for fewer side effects)
    • –Gene therapy – using normal genes to replace or supplement defective genes
    • Negative outcomes
    • - Genetic discrimination – insurance or employment
    • - Individual’s choice to want to know or not about a potential inherited dz.
  24. How can we modify a person’s genome?
    • Gene therapy - insertion of genetic material into human cells to treat a disorder
    • Ex vivo therapy – cells are removed from a
    • patient, altered and then returned to the patient
    • In vivo therapy – a gene is directly inserted into an individual through a vector (e.g. viruses) or directly injected to replace mutated genes or to restore normal controls over gene activity
    • Gene therapy has been most successful in treating cancer
  25. Who should have genetic testing?
    • If a family history of Cystic Fibrosis, genetic screening is recommended
    • –Test Parents (80-90% of carriers identified), fetus or child at birth
    • Early diagnosis does improve infant health and life expectancy
  26. In Vivo Gene Therapy
    • •Cystic Fibrosis – missing a gene that codes for the transmembrane carrier of Choride ion.
    • •Normal gene can be sprayed into nose or delivered to lower respiratory tract (adenoviruses or other vesicles)
    • •Working on improving uptake of normal gene
  27. Genius sperm bank
    • Repository for Germinal Choice, a sperm bank
    • for Nobel Prize winners
    • –It’s estimated that 230 children were born as a result
Card Set
Patters of Gene Inheritance
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