Card Set Information
Genetics Gene Inheritance
Patters of Gene Inheritance
One gene is able to express itself regardless of the presence of the other gene
Parents of individual may have not have the trait
Tends to skip a generation
May see consanguinity (blood relatives
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
the genes of the individual
the physical appearance of the individual
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
Genetic disorders of interest
Autosomal = non-sex chromosome
Autosomal Recessive Disorders:
: lack of the enzyme
: abnormal protein in cell membrane
: lack of an enzyme
: Abnormal RBCs
Autosomal Dominant Disorders:
: defect in elastic connective tissue;
: too many amino acids
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.
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
Cystic Fibrosis - Genetic disease causing lung and digestive problems
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
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
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
Newborns routinely tested for phenylalanine level in blood
Treatment is diet low in phenylalanine
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
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
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
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.
Males and females equally affected
Affected individuals have one affected parent
Characteristics may be present in all generations
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
--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
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
–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
- Genetic discrimination – insurance or employment
- Individual’s choice to want to know or not about a potential inherited dz.
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
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
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
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