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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

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Specialized mapping

Specialized Mapping

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/)


Physical chromosome mapping
Physical Chromosome Mapping

  • Somatic-Cell Hybridization

    Using human-rodent somatic cell hybrids to study the location of genes on chromosomes


Human-mouse hybrid cells with different

numbers of human chromosomes (blue).


Physical chromosome mapping1
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.


Problem 4 page 2 2
Problem 4, Page 2-2

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


Physical chromosome mapping2
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.


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


Tetrad analysis

Unordered Tetrad

Ordered Tetrad

Tetrad Analysis

  • Analysis of all four products of a single meiosis

  • Two Types of Tetrads



Genetic analyses with tetrads

a b

a+ b+

X

a b

a+ b+

Genetic Analyses with Tetrads

Cross two haploid cells

Induce diploid to undergo meiosis


Genetic analyses with tetrads1

a b

a b

Parentals

a+ b+

a+ b+

a b

a b+

X

Recombinants

a+ b+

a+ b

Genetic Analyses with Tetrads


M i segregation pattern

A first-division

segregation

pattern, MI

MI Segregation Pattern

No crossover between gene and centromere


M ii segregation pattern
MII Segregation Pattern

Crossover between gene and centromere



Producing m ii segregation patterns
Producing MII Segregation Patterns


Producing m ii segregation patterns1
Producing MII Segregation Patterns


Calculating genetic distances with tetrad analysis
Calculating Genetic Distances with Tetrad Analysis


Problem 2 page 2 1
Problem 2, Page 2-1

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.



Problem 2 page 2 12
Problem 2, Page 2-1

Distance from a centromere =

Distance from b centromere =

Distance from ab =


Problem 2 page 2 13
Problem 2, Page 2-1

Best solution


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