ged 12 Flashcards
what do physical maps show
distances between genes or dna markers based on the direct measurement of DNA
cytogenetic maps
indicate gene postions in respect to cytogenetic markers eg banding patterns
linkage maps
show the relative position of genes/markers ona chromosome, based on meiotic recombination frequecnies cM
locate genes along the chromosome based on crossing over frequencies
how many base pairs is one centimorgan
1 million
allels of genes on the same chromosome will segregate together unless
crossing over occurs between them
if two genes are close together what is the frequency of crossing over
low
crossing over results in ______ gametes
recombinant
independent assortment of genes on different chromsomes gives ___% recombinant gametes
50
if there are 50% recombinant gametes this tells us
the genes are located on different chromosomes
or are far apart on the same chromsome
less than 50% recombinant gametes tells us
the genes are linked on the same chrosmome
the smaller the recombination frequency, ___________))
the closer the genes are
how to determine genotype of gamete
make a double heterozygote
cross the double heterozygote to a tester (recessive ) strain
what is the genetic distance
RF recombination frequency
RF formula
number of recombinant progeny x 100/ the total number of progeny
units are cM
why aren’t genetic distances exactly additive
multiple crossover events underestimate the true distance eg double crossover can remove the recombinants
crossover in one region can influence another
