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Specialized Mapping

Specialized Mapping. Finding Chromosomal Locations Using Tetrad Analysis To Study Genetic Distances (see Tetrad Analysis PDF posted on eCompanion). Physical Chromosome Mapping. Somatic-Cell Hybridization

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Specialized Mapping

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  1. Specialized Mapping Finding Chromosomal Locations Using Tetrad Analysis To Study Genetic Distances(see Tetrad Analysis PDF posted on eCompanion)

  2. Physical Chromosome Mapping • Somatic-Cell Hybridization Using human-rodent somatic cell hybrids to study the location of genes on chromosomes

  3. Human-mouse hybrid cells with different numbers of human chromosomes (blue).

  4. Physical Chromosome Mapping • How can we determine which chromosome carries a specific gene? 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.

  5. Problems in Genetic Mapping #4 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. Human Enzyme Human Chromosome Hybrid Cell Line Hybrid Cell Line

  6. Physical Chromosome Mapping • How can we determine which portion of a chromosome carries a specific gene? 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.

  7. Gene is located on the short arm of Chromosome 4, in the region missing from Cell line 3 Enzyme Activity Present with intact Chromosome 4 Absent when short arm of Chromosome 4 is deleted Absent without Chromosome 4

  8. Unordered Tetrad Ordered Tetrad Tetrad Analysis • Analysis of all four products of a single meiosis • Two Types of Tetrads

  9. Producing an Ordered Tetrad

  10. a b a+ b+ X a b a+ b+ Genetic Analyses with Tetrads Cross two haploid cells Induce diploid to undergo meiosis

  11. a b a b Parentals a+ b+ a+ b+ a b a b+ X Recombinants a+ b+ a+ b Genetic Analyses with Tetrads

  12. A first-division segregation pattern, MI MI Segregation Pattern No crossover between gene and centromere

  13. MII Segregation Pattern Crossover between gene and centromere

  14. Types of Tetrads

  15. Producing MII Segregation Patterns

  16. Producing MII Segregation Patterns

  17. Calculating Genetic Distances with Tetrad Analysis

  18. Problems in Genetic Mapping #2 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.

  19. Problem #2

  20. Problem #2 Distance from a centromere = Distance from b centromere = Distance from ab =

  21. Problem #2 Best solution

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