Lec 12. Eukaryotic gene mapping Flashcards
What are the three mapping techniques?
Physical mapping, mapping with molecular markers and genome wide association studies
What are the two type of Mapping with molecular markers?
Haplotype and linkage disequilibrium
What do genome wide association studies deal with?
Associations within populations
What is a haplotype?
Set of DNA variation or polymorphisms that tend to be inherited together
Loci are said to be in linkage disequilibrium when
the frequency of association of their different alleles is higher or lower than what would be expected if the loci were independent and associated randomly
What haplotypes contribute to differences in huntington disease?
HTT haplotypes
What is another example of haplotypes when different can cause milder or more severe forms of the disease?
Sick cell anemia haplotypes.
Using crossover events to map gene location, what test can be used to map three linked genes?
Three-point testcross
What is coefficient of coincidence?
Number of observed double crossovers/number of expected double crossovers
What is interference?
1 - coefficient of coincidence
What are the 4 physical mapping methods used to determine the physical positions of genes on particular chromosomes?
- Physical and genetic maps differ. 2. Somatic-cell hybridization. 3. Deletion mapping. 4. physical mapping through molecular analysis (in situ hybridization).
What do both genetic and physical maps do?
Illustrate the arrangement of genes and DNA markers on a chromosome.
What is the difference between physical and genetic maps?**
Genetic map is based on crossing over, how many crossing over events can occur between 2 genes. Physical map is the actual nucleotide position of the genes.
What is a centimorgan?
Map unit measuring genetic linkage.
What does it mean when theres more centimorgans between two genes?
Further the distance between them and more crossing over between them.
Pertaining to physical mapping, what test can be used to determine which chromosome contains a gene of interest?
Somatic-cell hybridization
How would you do somatic-cell hybridization?
Get mouse and human cells together and they can fuse. Fairly stable and they realized that mouse chromosomes are telocentric and apparently mouse chromosomes are more dominant than human chromosomes and humans get kicked out. We have a cell that have mouse chromosomes and human chromosomes so if we have a marker and can extract it, then if we can identify the chromosome then we can identify that chromosome. Could establish a collection of lines, varies components of the human chromosomes.
What can deletion mapping be used to determine?
To determine the chromosomal location of a gene
What is the idea of deletion mapping?
The idea is that a gene happens to occur in a deleted region, if we can connect the phenotype to that deleted region we can say this is what happens
What is one ex of a disease that was found with deletion mapping?
Duchenne muscular dystrophy. By looking at g banding on the boys with ducheenes they noticed some of them had deletions and that all deletions happened in the same spot on the X chromosome.
What is in situ hybridization used for?
Another technique used for determining the chromosomal location of a gene
What is an example of situ hybridization?
FISH.
How is the test FISH done?
DNA probe containing gene is dyed with fluorescent dye and then hybridized to interphase or metaphase cells.
What does FISH detect?
Small regions of deletions or duplication
