Linkage 7.2 Flashcards
Unlinked loci follow _____
Independent assortment
Linked loci travel together during____
Meiosis
Recombination frequency
measure of how frequently recombination occurs between 2 loci
Complete linkage: RF =0%
No recombinant gametes are produced
Partial linkage: 0<RF<50%
Some recombinant gametes are produced, but fewer than you would expect
Unlinked: RF are = 50%
Linked: RF are <50%
During prophase I, homologous chromosomes are paired together tightly through a process called
synapsis
What happens during synapsis?
Homologous regions of chromatids are cut (“restricted”) and pasted (“ligated”) back together
This results in exchange of DNA between homologous chromosomes
Where does recombination occur?
Between identical sequencies on homologous chromosomes
DNA is cut at the same position on homologous chromosomes
Chromatids exchange ends and glue them back together
No DNA is lost or genes
Occurs ~1-3 times per arm per chromosome per meiosis
What does “phase” or “gametic phase” represent
The allele combinations that were inherited from each parent
Linkage will lead to more (parent or non parental) phases in offspring
parental
Thomas Hunt Morgan
Observed that sometimes there were “non-parental” gametes and suggested that chromosomes may be recombining
Harriet Creighton and Barbara McClintock
Discoverers of recombination
Genetic Distance= Recombination Frequency
What is equation?
RF= # of recombination events/total progeny *100
