Gene Mapping Flashcards
What is the clinical triad of cystic fibrosis?
Exocrine pancreatic insufficiency
COPD
Elevation of sodium and chloride concentration in sweat
What is positional cloning?
the approach of cloning a gene purely on the basis of its map position, without knowing much, if anything, about what the gene does or what its molecular function may be
What is the Genome-scan linkage approach?
A large set of genetic markers spaced every 0.5 cM is used to test for gene linkage
Used in conjuncture with the candidate gene approach.
What is the Candidate gene approach?
if a gene is suspected to lie in a particular region, then you can directly test for linkage of this gene to markers in the region
Used with genome-scan linkage
What is the LOD score (maximum likelihood) method?
Maximum likelihood analysis allows one to determine if two genes (or markers) are linked and what the genetic distance is between them
What is a LOD score?
the logarithm of the ratio of the likelihood that a given pedigree can be obtained given a recombination frequency
What is the interpretation rule?
If the LOD score or ratio (Z) is > or = 3, then the genes are linked.
If it is < or = -2, then the genes are not linked
Anything in the middle of -2 and 3 is insignificant
What are three problems with genetic mapping in humans?
Loci must be informative = need heterozygosity at both the marker locus and disease gene locus
Need to know the phase to be able to count recombinants
The percent recombination is only accurate over short distance
What is a cytogenetic map?
Places genes into specific cytogenetic bands of the karyotype
What is a Linkage or Genetic Map?
Orders genes and genetic markers by recombination distances, i.e. cM
What is a physical map?
Orders genes and genetic markers along the DNA strand of a particular chromosome. Distances measured in kb
What is a restriction fragment length polymorphism?
Variations occuring within a species in the length of DNA fragments generated by a specific endonuclease.
Generated by mutations that create of abolish recognition sites for these enzymes.
