Lec 10-3 Flashcards
Genetic markers
Variable genes with easily observable phenotypes whose inheritance can be studied
Fruit flies genetic markers
Large efforts using genetic markers mapped a lot of gene loci on all 4 chromosomes
This is a miniscule amount compared to the genome
Gene mapping finds
Where genes are physically on the chromosome
Physical mapping methods aim to
Create physical maps of genes on chromosomes and do not depend on recombination frequencies
Deletion mapping
Chromosomes can be stained and have characteristic banding patterns
Absence of one or more bands indicates large deletions
How deletion mapping works
If you have strains that are mutant for a trait of interest but gene and chromosomal location that is responsible is unknown
Genetic crosses between mutant strain and a panel of deletion strains (chromosome with a deletion) to physically locate the genetic cause
Strain usually homozygous recessive for mutant allele
Cross between mutant strain and deletion strain
50% progeny will be heterozygous for mutant over deletion
50% will be heterozygous for mutant over wild-type chromosome
Cross between mutant strain and deletion strain
If gene A is located in the deleted region of one strain and not the other
Expect half the progeny from strain 1 to have a mutant phenotype, but no mutant phenotype present in strain 2 cross
By using deletion strains that “tile” the chromosome
You can precisely make a physical map of gene locations
Direct Physical Mapping using FISH
FSH stands for
Fluorescence in situ hybridization
FISH
Generate small DNA/RNA probes complementary to sequence in the genome
Nucleotide probe is fused to fluorescent probe
Can visualize directly where the gene is located on the chromosome
Recombination rates variability
Variable across the chromosome
Vary across species
Vary between male and female (eg. Male fruit flies have no recombination)
