Diagnostic Genetics - Campbell Flashcards
What are three forms of prenatal genetic diagnosis of inherited disease utilized that together cover most of the period between 10 weeks gestation through birth? What is the typical rate of fetal loss associated with each?
CVS (chorionic villus sampling): 0.5 to 1.0%
Aminocentesis: 0.25 - 0.5%
Cordocentesis (percutaneous umbilical cord blood sampling) : 1-2%
What does preimplantation diagnosis of in vitro fertilized eggs allow?
Allows for DNA sampling to look for specific genetic diseases and have parents be able to choose a fetus without a genetic disease (like Tay Sachs)
What do diseases screened for by the Florida newborn screening program have in common that makes them a good idea to screen for? What instrument made possible the recent expansion in the number of diseases screened for in Florida?
Does it analyze DNA sequences or metabolites?
All Newborn screen diseases have the following common criteria:
1) Early intervention is key
2) Successful intervention is available
Tandem Mass Spectrometer allowed for the expansion of number of diseases screened for in Florida.
It analyzes metabolites. (Sarah)
What is the way in which a specimen is collected for the newborn screening in Florida. What are some specimens from which DNA is easily obtained from children and adults?
Cord Blood is taken at 8-16 weeks.
In adults, DNA can be taken via saliva, cheekswabs, and blood. In Children, DNA can be taken via blood.
What are the disadvantages of screening for genetic diseases by gaining DNA sequence information? What are the advantages?
Advantages:
- may catch a patient that gives a false negative by another test
- Easier, less expensive in quantity
- Predictability w/ family history aiding targeting
Disadvantage:
- False Negatives from gene mutation in unexpected location
- Limited coverage
- Sequence based tests have added expense
What rough % frequency are the two most often occurring mutations known in the CFTR gene? What is the ramification of this for detecting cystic fibrosis by screening for mutations? Are there any high frequency mutations in the LDL receptor gene? What is the ramification of this for detecting familial hypercholesterolemia by screening for mutations?
70% of Cystic fibrosis patients have an easy to spot mutation. (67% a change in Phenylalanine; 2% a missense)
No high frequency LDL mutations, no detecting for hypocholesteroemia as there are too many mutations with no high frequency. Edited by Sarah.
- You have a 27 year old patient whose father has just been diagnosed with Huntington disease. It would be important to
A. immediately begin aggressive treatment to prevent the disease.
B. have them perform co-ordination tests to see if they have Huntington disease.
C. advise the patient that because their brother (age 35) is suffering from Huntington disease that they are at minimal risk.
D. advise the patient to have a panel of biochemical tests to test enzyme levels carried out to determine if they will get the disease.
E. tell the patient that there is a test involving DNA sequencing to show if they also will suffer from Huntington disease later in life.
E. tell the patient that there is a test involving DNA sequencing to show if they also will suffer from Huntington disease later in life.
