Chapter 7
Genetic Linkage and Mapping in Eukaryotes
Study Outline
1. Overview of linkage
a. Bateson and Punnett discovered two traits that did not assort independently
2. Relationship between linkage and crossing over
a. Mitochondria Crossing over may produce recombinant genotypes
b. Morgan provided evidence for the linkage of X-linked genes and proposed that crossing
over between X chromosomes can occur
c. The likelihood of crossing over between two genes depends on the distance between
them.
d. A chi square analysis can be used to distinguish between linkage and independent
assortment
e. Creighton and McClintock showed that crossing over produced new combinations of
alleles and resulted in the exchange of segments between homologous chromosomes
3. Genetic mapping in plants and animals
a. The frequency of recombination between two genes is used to compute map distance
along a chromosome
b. Alfred Sturtevant used the frequency of crossing over in dihybrid crosses to produce the
first genetic map
c. Trihybrid crosses can be used to determine the order and distance between linked genes
d. Interference can influence the number of double crossovers that occur in a short regiond
4. Mitotic recombination