Gene Mapping - case study of CF Flashcards
Deletion mapping
A homozygous recessive individual is crossed with an individual heterozygous for a deletion. If the gene is in the deleted region, half of the progeny will display the phenotype. If not, all will be wild type.
Heterokaryon
Human fibroblasts fused with mouse tumor cells. Results in loss of different human chromosomes.
Clinical aspects of cystic fibrosis (9)
- Predominantly affects northern Europeans
- Affects epithelia in several organs: pancreas, intestine, respiratory tract, male genital tract, hepatobiliary system, and the exocrine sweat glands.
- Pulmonary disease is the major cause of morbidity and mortality in CF: airway inflammation and chronic endobronchial infection.
- Liver disease: elevation of liver enzymes in serum
- Patients with pancreatic sufficiency (<10%) have a milder clinical course with greater median survival (i.e., 56 years) than those with pancreatic insufficiency.
- Median survival in 2003 was 26.9 years
- Variability of disease expression due to varying severity of CFTR mutations, genetic modifiers, and environmental factors.
- More than 95% of males with CF are infertile
- Women with CF are fertile
Haplotype
Combination of SNPs commonly found together - can be used to map disease genes
RFLP
Restriction fragment length polymorphism - polymorphism that results in different sized fragments when cut by a restriction enzyme
VNTR
Variable number of tandem repeats (minisatellite) - 10-60 bps
STR
Short tandem repeat (microsatellite) - 2-6 bps
LOD Score
Logarithm of Odds scores - measures recombination between a marker and a disease gene
likelihood of non-random segregation divided by likelihood of random segregation
LOD 3 = 1000:1 odds, significant level
Steps to finding a gene
Identify the region using markers
Identify the coding region using promoter and splice site pattern recognition
in silico mapping
Map using genome databases on a computer
Proofs of association and causality
Compare affected and unaffected individuals by RNA size or quantity, or any mutations
Retrovirus
RNA virus that have been integrated into the host genome using reverse transcriptase