22. Linkage mapping and Association Flashcards
define a linked gene
genes which are close together on the same chromosome
define an unlinked gene
Alleles positioned on the same chromosome are not always inherited together because during meiosis linked genes can became unlinked
define a sex linked gene
genes on the x and y sex chromosomes
what does the recombiation frequency measure? what is the equation? what is the maximum it can go?
the amount of crossing over between two genes.
recombination/ total x 100 = RF
never goes over 50%
what are parental types offspring?
offspring that have the same combination of alleles on each chromosme as their parents.
define recombinant types
offsping that are due to new combinations of alleles not found in the dihybrid parent which is produced as a result of crossing over in meiosis
study image!
what is crossing over/recombination
recombination of linked genes - occurs while replicated homologous chromosomes are paired during prophase of meiosis 1, a set of proteins initiate an exchange of segments of one maternal and one paternal chromotid.
two nonsister chomatids trade places
what is the lower proportion, recombinant types or non-recombinant phenotype?
recombinant types!
what is a genetic map?
an ordered list of the genetic loci along a particular choromosome. the farther away two genes are, the higher the probability that a crossover will occur between them and therefore the higher the recombination frequency
what are genetic markers?
detectable sequences in the DNA that are inherited along with the diseased gene. it is a known location on a chromosome
what is a single nucleotide polymorphosis? (SNP)
base substitution variations in the genomes of the population. its a signle base-pair site where variation is found in at least 1% of the population. is used to locate genes in family studies or populations
how are SNP’s used for finding genes associated with disease phenotypes?
they are used to find genes. so if most people who develop heart disease have a G base at a particular SNP sit, while other dont, the SNP site is use as an indicator of suspectibilty for a disease.
