Specialized Mapping. Finding Chromosomal Locations Using Tetrad Analysis To Study Genetic Distances (see Tetrad Analysis Web Module for Chapter 7 on Text Web Site http://whfreeman.com/pierce/ ). Physical Chromosome Mapping. Somatic-Cell Hybridization
Finding Chromosomal Locations
Using Tetrad Analysis To Study Genetic Distances(see Tetrad Analysis Web Module for Chapter 7 on Text Web Sitehttp://whfreeman.com/pierce/)
Using human-rodent somatic cell hybrids to study the location of genes on chromosomes
numbers of human chromosomes (blue).
In human-mouse hybrid cells, a 1:1 correspondence exists between the presence of the enzymatic activity for the gene and the presence of the chromosome carrying the gene.
Hybrid cells containing human and mouse chromosomes were analyzed. The grid on the left shows the presence or absence of each of four human chromosomes in hybrid cell lines A through D. The grid on the right shows the presence or absence of human enzyme activity in each of the cell lines. Assign the gene for each enzyme to the chromosome that carries the gene.
Hybrid Cell Line
Hybrid Cell Line
If the enzymatic activity is present in a cell line with an intact chromosome but missing from a line with a deletion in that chromosome, the gene for the enzyme is in the deleted region.
Gene is located on the short arm of Chromosome 4, in the region missing from Cell line 3
Present with intact Chromosome 4
Absent when short arm of Chromosome 4
Absent without Chromosome 4
Ordered TetradTetrad Analysis
a+ b+Genetic Analyses with Tetrads
Cross two haploid cells
Induce diploid to undergo meiosis
a+ bGenetic Analyses with Tetrads
pattern, MIMI Segregation Pattern
No crossover between gene and centromere
Crossover between gene and centromere
In a Neurospora cross of ab x a+b+, the following classes and numbers of tetrads were produced. Neurospora produces ordered tetrads that undergo a single mitosis after formation. Pairs of spores are listed below for simplicity.
Distance from a centromere =
Distance from b centromere =
Distance from ab =