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B2 Gene12/11 L 11y12

Cytogenetics y Genetic Screening

QuestionAnswer
At what age do pregnant mothers start having an elevated risk of birth defects maternal age 35 or greater >> increased risk for Down’s syndrome and other non-disjunctions
What are major indicators that their is an elevated risk of birth defect? 1. maternal age 35 or greater 2. previous child with a de novo chromosomal abnormality 3. presence of a structural chromosomal abnormality in a parent 4. family history of a genetic disorder
What two techniques can be used to detect possibility of chromosomal disorder in low risk mothers examination of maternal serum or ultrasound
What are the three invasive methods of obtaining cells fetal cells for analysis amniocentesis, chorionic villus sampling , and percutaneous umbilical cord blood sampling
What is amniocentesis? it is where a syringe is inserted through abdominal wall to remove 20-30 ml of amniotic fluid
When can an amniocentesis be performed? week 16, because there is not enough amniotic fluid until week 16 gestational age
What types of cells would you find in amniotic fluid? skin and lung cells
How is the amniotic fluid typically analyzed? The cells (skin and lung) are isolated and cultured. The amniotic fluid itself is sometimes analyzed – ex. high levels of alpha–fetoprotein indicative of neural tube defects and other disorders
What are two major advantages of chorionic villus sampling over amniocentesis? 1. cells from a chorionic villus sampling are already readily dividing so a karyotype can be done quickly without a culture (2) A chorionic villus sample can be taken earlier (10-12 weeks) than amniocentesis (16 weeks)
What are the two ways a chorionic villus sampling can take place? biopsy needle can be inserted through either the abdominal wall or through vagina to obtain sample of chorionic villus
List the prenatal diagnosis techniques in order of risk from least risk to most risk amniocentesis (lowest risk), chorionic villus, and percutaneous umbilical cord blood sampling (highest risk)
When can percutaneous umbilical cord blood sampling be preformed? By week 20
Besides the actual technique how does percutaneou umbilical cord blood sampling differ from amnicentesis and chorionic villus samping? It is rarely done solely for karyotyping purposes, though it gives access to white blood cells, the cell typically karyotype
What is genetic screening, and how does it differ from genetic testing? genetic screening is a population based method for identifying persons with certain genotypes known to be associated with a genetic disease or predisposition to a genetic disease. It differs from genetic testing due to size of pop. testing < screening
What are some examples of things that are genetically screened for? phenylketouria (all 50 states), galactosemia, congenital hypothyroidism (non-genetic) and sickle cell
What is the disease criteria for a screening program? 1. high incidence in target pop. 2. serious effect on health 3. tratable or preventable
What is the criteria for tests utilized in a screening 1. non-invasive and easily carried out 2. accurate and reliable 3. inexpensive
What is the criteria for a screening program? 1. widespread and equitable availability 2. Voluntary participation 3. acceptable to the target population 4. full information and counselling provided
What is the only major proposal for adult genetic screening? hemochromatosis ( autosomal recessive disorder cause by iron overload which leads to permanent organ damage). It is successfully treated by repeated phlebotomy, and tested by serum iron-transferrin levels
What is heterozygote screening? tests for healthy individuals who are at risk for having affected children
What are somethings typically tested by way of heterozygote screening? Tay Sachs disease among Jews of eastern European descent. (incidence lowered from 85% to 65% as a result) Beta–thalassemia in Cyprus (successful reduction of incidence) sickle cell in African Americans (no decrease in incidence)
What is typically tested for in a prenatal screening Only standard screening in maternal serum is for alpha-fetoprotein (nuerotube defect) and fetal karyotyping with advanced maternal age (ex. trisomy 21 - down syndrome)
Created by: VCOM2013 on 2009-12-15



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