Lecture 3 Flashcards
What are the three types of genetic testing?
Direct testing, Cytogenic testing, Biochemical testing
What is direct testing?
Looking at the DNA or RNA that makes up a gene
What is a Cytogenetic test?
When the chromosomes are examined
What is biochemical testing?
When you assay for particular metabolites
What are the two uses of genetic testing?
Diagnostic and Predictive
What is the purpose of predictive testing?
So that potentially life style changes can be made in order to improve the health outcome
What are the two forms of genetic heterogeneity?
Locus Heterogeneity and Allelic heterogeneity
What is locus heterogeneity?
When multiple mutations can cause the same phenotype from different loci
What is allelic heterogeneity?
many mutations within the same gene can result in different phenotypes
What is the concept of penetrance?
How likely it is that the gene will result in a phenotype as it can vary dramaticallly between individuals
What is expressivity?
The idea that a gene will manifest itself in different ways between individuals even if the gene is identical
What is the process of Prenatal Diagnosis?
when chromosomal and genetic analysis is achieved through either culturing cells from amniotic fluid or through analyisis of homrones or proteins in the mothers blood etc
What are the non-invasive prenatal diagnostic methods?
Maternal Serum alpha-fetoprotein,
Maternal serum screen,
Ultrasonography
What does Maternal Serum alpha-fetoprotein test for?
Tests for levels of AFP which are elevated in neural tube defects and reduced in downs syndrome
What does the maternal serum screen test for?
AFP to detect neural tube defects/downs syndrome
High levels of hCG and inhibin A are seen in downs syndrome
Oestriol is low in downs syndrome
What are the two methods of invasive prenatal diagnosis?
Amniocentesis
Chorionic Villus Sampling
How does the test of amniocentesis work?
A small amount of amniotic fluid is collected for studies
How does Chorionic Villus Sampling work?
Biopsy is performed on the villus area of the chorion either transabdominally or transcervically
What is the advantage of chorionic villus sampling as opposed to amniocentesis?
Results can be obtained at an earlier date
What is pre implantation diagnosis?
Several embryos are cultured and then are tested through FISH and other genetic techniques and only those found without mutations will be implanted
What are the two key things required to prove that a gene is linked to a disease?
Mutation screening and Functional proof
What is mutation screening?
Failure to notice the gene in a large sample of controls
The gene can be observed with a clear and relevant inheritance pattern in a pedigree chart
What is functional proof with regards to linking a gene to a disease?
There must be proof thorugh things such as computer modelling that the change the mutation has on the final product is important or relevant with regards to the original proteins function
What is the only currently avaliable treatment for those with genetic diseases?
Primary prevention where changes in lifestyle or potentially some drug treatments may prevent onset of the disease
