Gene Mapping - case study of CF

Question 1

Deletion mapping

Answer 1

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.

Question 2

Heterokaryon

Answer 2

Human fibroblasts fused with mouse tumor cells. Results in loss of different human chromosomes.

Question 3

Clinical aspects of cystic fibrosis (9)

Answer 3

• 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

Question 4

Haplotype

Answer 4

Combination of SNPs commonly found together - can be used to map disease genes

Question 5

RFLP

Answer 5

Restriction fragment length polymorphism - polymorphism that results in different sized fragments when cut by a restriction enzyme

Question 6

VNTR

Answer 6

Variable number of tandem repeats (minisatellite) - 10-60 bps

Question 7

STR

Answer 7

Short tandem repeat (microsatellite) - 2-6 bps

Question 8

LOD Score

Answer 8

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

Question 9

Steps to finding a gene

Answer 9

Identify the region using markers

Identify the coding region using promoter and splice site pattern recognition

Question 10

in silico mapping

Answer 10

Map using genome databases on a computer

Question 11

Proofs of association and causality

Answer 11

Compare affected and unaffected individuals by RNA size or quantity, or any mutations

Question 12

Retrovirus

Answer 12

RNA virus that have been integrated into the host genome using reverse transcriptase