CHP 7: Genetic Linkage and Mapping in Eukaryotes

Linkage

Refers to the state of two genes being on the same chromosome, so they are physically linked to each other

Synteny (Syntenic Genes)

Genes are linked by being on the same chromosome

Genetic linkage cause issues with the Law of Independent Assortment

True

Genetic linkage does not cause issues with the Law of Independent Assortment

False

Locus

Refers to a location within a chromosome related to a phenotype

A gene occupies a physical position of a chromosome; as a result, genes are sometimes called a _____

Locus

Recombinant Offspring

Offspring do not have the same combination of phenotypes as found in parents

Recombinant offspring can be produced by…

The independent assortment of unlinked genes

Thomas Hunt Morgan studied…

Fruit flies

What did Thomas Hunt Morgan’s study on fruit flies explain?

How linked genes can recombine

Crossover

Allows alleles to switch from one homologous chromosome to another

Parental Combination (non recombinant)

The original combination of alleles

Recombinant Combination

The combination of new alleles as a result from crossover

Homologous Recombination

In meiosis I, homologs interact and genetic information can cross over

Recombinant Phenotypes

Genetic information crossover

In recombinant phenotypes when genes are linked…

Those genes separate together (A remains linked to B, a remains linked to b)

In recombinant phenotypes when a crossover events takes place somewhere between the loci…

The alleles switch positions (A is now linked to b, B is now linked to a)

Thomas Hunt Morgan determined that recombination rate depends on…

Distance (if two loci are far apart, it is likely that a random crossover events takes place occurs between them compared to if they were closer)

Calculate Recombination Frequency

Recombination Frequency = (# of recombinant offspring / total # of offspring) x 100

Recombination frequency relates to…

Distance

Low recombinant frequencies indicate…

Genes are closer together

High recombinant frequencies indicate…

Genes are far apart

Calculate Map Distance

Map Distance = (# of recombinant offspring / total # of offspring) x 100