Northern Information and Courses from MediaLab, Inc.
These are the MediaLab courses that cover Northern and links to relevant pages within the course.
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| Blotting Techniques Blotting techniques were developed to discriminate fragments of nucleic acids. These techniques involve several processes; electrophoresis is one of the processes and is used to separate fragments of DNA and RNA. In Southern blotting (named after Edward Southern) restriction enzymes cut fragments of DNA are separated by AGE or PAGE, transferred to a membrane or blot, and visualized by hybridization with labeled probes.Northern blotting (not named after an inventor but by analogy to Southern blotting) separates RNA. RNA molecules are shorter and have defined lengths; cutting by restriction enzymes is not required. Denaturing conditions are required because of RNA secondary structures. After membrane blotting, the separated types of RNA are visualized with staining or labeled probes.Western blotting (again not named after an inventor but by analogy to Southern blotting)does not separate nucleic acids; it separates proteins in a mixture. The proteins are usually separated with PAGE, transferred to the membrane and visualized with a labeled antibody against the proteins of interest. | View Page |
| Direct Nucleic Acid Tests Southern Blot: Employs a restriction endonuclease enzyme to extract DNA from the cells. DNA detection is done using agarose gel electrophoresis.Fluorescent In Situ Hybridization (FISH): Uses RNA Northern Blot or DNA Southern Blot techniques to detect targets of interest in cytology/histology specimens or other nucleic acid variations. DNA fingerprinting: Restriction Fragment Length Polymorphism (RFLP): Cuts long DNA into shorter fragments before detection to isolate changes or polymorphisms. These can either be detected by Southern Blot or by Polymerase Chain Reaction (PCR). | View Page |
| Match the following tests to their appropriate principle: | View Page |
| Prevalence of HFE The C282Y mutation is common in the Caucasian population, especially in people of northern European descent. Approximately 10% of Caucasian Americans are heterozygous carriers of a single C282Y mutation.(8) A greater percentage are carriers of the H63D mutation, but this mutation is much less clinically significant. Hereditary hemochromatosis appears to be most prevalent among people in the Northern British Isles--Scotland, Ireland and Great Britain--who are of Celtic descent. Persons of Celtic descent in the United States, Australia, and France also have a relatively high incidence of HH. The prevalence of HFE mutations in African Americans and Hispanic Americans is low. | View Page |
| Screening Controversies The subject of screening for hereditary hemochromatosis (HH) is controversial and is currently being debated in the medical literature. Using laboratory tests to screen the asymptomatic general population is currently not recommended due to issues of testing costs, low genetic penetrance, and the possible risk of discrimination. Targeted case finding in select high risk populations such as men of Northern European ancestry may be a better approach to screening. (12)Molecular-based (DNA) assays required for confirmation of HH are costly when used for general population screening. Because recent studies have shown that a high percentage of persons with C282Y mutations do not develop iron overload or HH-related clinical conditions, screening for these mutations may falsely label an individual with a disease diagnosis. At the present time, it is impossible to determine which homozygotes or heterozygotes for HFE mutations will eventually develop iron overload. Furthermore, there is potential risk of discrimination in obtaining health insurance for persons identified as having genetic disorders.In contrast, some experts do advocate for screening the general population. Mutations associated with HH are very common in Caucasians in the US. Individuals who know they carry mutations associated with HH may benefit from periodic testing for iron overload. Finally, laboratory tests that assess iron status are relatively inexpensive, widely available, and offer one approach to screening for phenotypic expression of HH. Screening first-degree family members of a person with documented HH is generally considered to be worthwhile. Early detection of HH in relatives with common mutations may permit treatment before the development of substantial iron overload and related disease due to organ damage. | View Page |
| Match the names of each of the diseases listed with its appropriate situation: | View Page |