Genetic Conditions: PKU & Cystic Fibrosis Flashcards
Explain the importance of genetic testing in biomedical research.
Genome analysis is rapidly becoming an important tool in biomedical research and promise to make a substantial impact on global health.
Genetics is involved in conditions such as Gout, Lesch-Nyhan Syndrome, Ehlers Danlos Syndrome & Acromehaly.
What are some features of metabolic disease?
Sufferers show darkening urine fro yellow to brown to black after it is exposed to the air. In later life, individuals with this disease develop arthritis characterised by deposition of brown pigment in joint cartilage and connective tissue.
The Tyrosine Catabolism pathway is involved in the metabolic disease.
Explain the difference between genotype and phenotype?
Phenotype: physical appearance of the individual with regard to a trait
Genotype: two alleles for a trait; can be either dominant or recessive. Dominant does not mean frequent.
Explain some features of colour blindness
Mutations in the CNGA3, CNGB3, GNAT2, OPN1LW, OPN1MW, and OPN1SW genes restrict the range of colours that stimulate cone-cells.
The most common red-green colour blindness is X-linked recessive. In Australia men have 8% incidence, women 0.4%. Blue-Yellow colour blindness is autosomal dominant.
What are some features of X-linked recessive conditions?
X-linked recessive conditions include common male pattern baldness and the serious diseases Hemophilia A, Duchenne muscular dystrophy, Lesch-Nyhan syndrome.
What are Mendel’s first and seconds laws?
Mendel’s First Law:
Parents have 2 copies of a gene for a character. There are two copies because of paired chromosomes (diploid).
Genes that code for a functioning protein are typically dominant e.g. the gene for Huntington’s chorea.
Parents pass one gene to their progeny because meiosis assorts only one of a chromosome pair to a gamete (haploid).
Mendel’s Second Law:
Different characters are inherited independently.
Except for characters on the same chromosome (linked characters), but Mendel did not know that.
Linkage is now known from the human genome project.
Linkage was historically important in finding the genes for Cystic Fibrosis and Duchene’s Muscular Dystrophy.
What are Developmental errors apparent at birth?
Developmental errors apparent at birth are congenital. Anomolies may or may not have a genetic basis. An example of this is Thalidomide which is a racemic mixture and not a genetic condition.
What are some features Phenylketonuria (PKU)?
If not treated within the first few weeks of life it can cause mental retardation, seizures, tremors and behavioral disorders.
It is a lack of phenylalanine hydroxase. In PKU elevated phenylpyruvate damages the brain and inhibits tyrosinase the melanin making enzyme.
What are some features of Cystic Fibrosis?
Cystic Fibrosis (CF) is the most common life-threatening genetic disorder in Australia with an incidence of 1 in 2,500 births. CF primarily affects the respiratory system (lungs), digestive system (pancreas and sometimes liver) and reproductive system. CF causes a build up of mucous in the lungs which may lead to repeated chest infections. Lung damage may result, reducing lung function. Most people with CF have a persistent cough to clear away mucous secretions in the lungs.
What are some features of Marfan Syndrome?
Skeletal system involvement is characterized by bone overgrowth and joint laxity. The extremities are disproportionately long for the size of the trunk (dolichostenomelia).
The fibrillin1 gene FBN1 is mutated in Marfan syndrome. FBN1 produces a protein which is transported out of the cell and deposited in the extracellular matrix. Fibrillin becomes part of microfibrils, which in turn help build elastic fibres essential for the function of flexible structures such as blood vessels, the lungs, and skin.
Patients with Marfan syndrome show decreased production of fibrillin-1, delayed transport of the protein out of the cell, or reduced amounts of the protein in the extracellular matrix.
