P1 P2 : Parental strains.

Homozygous at all loci,but differing in phenotype.

F1: First filial.

Heterozygous at all loci.Breed with one another to get F2.

F2: Second filial.

Recombination in F1 gametes gives a mixtureof P1 and P2 chromosome sections.

P1 P2 : Parental strains.

Homozygous at all loci,but differing in phenotype.

F1: First filial.

Heterozygous at all loci.Breed with one another to get F2.

Recombinant Inbred Strains:Step 1: Initial Mendelian Cross

P1 P2

Recombinant Inbred Strains:Step 2: Sib-matings

× × × ×F2

× × × ×F3

× × × ×FA Lot

Recombinant Inbred Strains:Phenomenon 1: Recombination will break

up the red versus blue segments. Note how thereis more red/blue combinations in F3 than in F2.

× × × ×F2

× × × ×F3

Recombinant Inbred Strains:Phenomenon 2: Sib matings increase

homozygosity. After a large number of generations (20 is close to “large”), one creates

inbred strains that are identical at all loci.

× × × ×F3

× × × ×FA Lot

Common Sense Explanation:

Recombination breaks up the red versus blue areas.

But within a line of sib matings, the SAME red/blue combinations are transmitted and,

after a long time, become homozygous..

At each locus, ½ of the strains should be rr and the other 1/2will be bb. Do a t-test using phenotypic scores as thedependent variable and genotype ( rr versus bb) as the group variable.

If the test is significant, then that gene (or more likely, a geneclose to the genotyped locus) influences the phenotype.

A more complicated approach would use haplotypes.

Recombinant Inbred Strains:Linkage Analysis