exam 2: linkage, recombination, gene mapping Flashcards
what does it mean when genes are unlinked?
genes (loci) segregate independently
what does it mean when genes are linked?
not all genes segregate independently
-if 2 specific alleles from 2 diff loci are inherited tgt more often than expected, the 2 loci are linked
what causes linkage? (for unlinked genes)
two loci close tgt on same chromosone
what does syntenic mean
loci that are same chromosome regardless of linkage (can be linked/unlinked)
*all linked genes are syntenic, but not all syntenic genes are linked
an example of a linked gene
body color gene and eye color gene in fruit fly
the body color gene and eye color gene is close tgt on X chromosome
mutant w: recessive= white eyes
wt:red
mutant y: recessive=yellow body
wt:brown
if genes are on the same chromosome, how are new genotypes produced?
recombination
-recombinants: gametes resulting from recombination (not same config as parent)
if genes are unlinked, what do u expect to see?
and if they are linked, what do u expect to see?
unlinked: 25 % of each different gamete
linked: more parental types and few recombinant types
why? recombination less likely to occur between 2 genes tgt on same chromosome
how can you test if two genes are linked?
set up cross where recombination can be observed if it happens
what statistical test could you use to determine the significance of the difference?
chi square
whats the maximum difference distance between 2 linked genes?
two linked genes can never be separated by more than 50 mu
-max rate if recombination between 2 genes on same chromosome does not exceed 50%
why?
if 2 genes on same chromosome experience reconbination between 50% of the time
what are linkage groups?
any group of genes linked on the same chromosome
