Gene Mapping

Geneticists use maps to describe the location of a particular gene on a chromosome. One type of map uses the cytogenetic location to describe a gene’s position. The cytogenetic location is based on a distinctive pattern of bands created when chromosomes are stained with certain chemicals. Another type of map uses the molecular location, a precise description of a gene’s position on a chromosome. The molecular location is based on the sequence of DNA building blocks (base pairs) that make up the chromosome.

Cytogenetic-- e.g. 17q12 17th Chromosome, q for long arm --p would be short and 12 for position.  If vague might say  17q12-q21

<img src="/9cec4067-699a-5907-9ef6-57aa837d1e2e.png"/>      e.g. for Cystic Fibrosis the CFTR gene is located 7q31.2  Long arm of Chromosome 7 at position 31.2

The human CFTR gene's full name is:

Cystic Fibrosis Transmembrane Conductance Regulator, ATP-binding cassette, sub-family C,  member 7.

The gene CFTR codes for the protein CFTR (Cystic Fibrosis Transmembrane Conductance Regulator). The CFTR protein functions as an ion channel across the cell membrane. The CFTR protein is present in tissue that produces mucus, sweat, saliva, tears, and digestive enzymes.

The CFTR protein regulates the flow of chloride, a component of salt, in response to cellular signals. The transport of chloride controls the flow of water in and out of tissues; water content maintains the fluidity of mucus.  

CFTR Gene Mutations:

Over 1000 mutations have been found in the CFTR gene.  Although, the majority of mutations are not associated with CF. The most common mutation is called ΔF508, a deletion of phenylalanine at position 508. This mutation causes the most common CF symptoms.

This altered protein never reaches the cell membrane, as it is recognized as defective and destroyed shortly after it is made. All serious mutations in the CFTR gene prevent the CFTR protein channel from functioning properly. An ill-functioning CFTR protein blocks the movement of salt and water into and out of cells. This causes the tissue to secrete an abnormally thick mucus, which causes the symptoms of CF.

Molecular Location Mapping--

Figure 1. Circular map of plasmid pEC302/04. The 1st (innermost ring) and the 6th rings show the plasmid size in kbp. The 2nd and 3rd rings (from inner to outer) show the GC skew (purple) and GC content (black), respectively. The 4th and 5th rings show the ORFs in forward (blue) and reverse orientation (red). The outermost ring shows the important genes encoding regions highlighting with different colors according to its function: orange, replication; pink, transfer region; yellow, addictive systems; red, iron acquisition systems; blue, antimicrobial resistance; green, other virulence factor; gray, IS elements.

Gene Mapping

Attachments