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Lecture 11

BIOLOGY 2C03 Lecture 11: 11) Module 5 cont
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6 Pages
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Department
Biology
Course Code
BIOLOGY 2C03
Professor
Bhagwati Gupta

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11) Module 5 cont Thursday, October 6, 2016 12:26 PM 17 Diseases detected using polymorphisms. How polymorphisms are identified in individuals using blood samples. Useful for mapping diseases. - - Polymorphism MUST lie very close to the gene, and a particular varient near the disease causing allele (mutation in that gene). - If you can find a polymorphism tightly linked to the gene, the polymorphism location will allow you to find the gene. - If close, they are strongly linked and crossing over will NOT occur - If far away, not useful due to recombination - polymorphism will dissociate from the allele. 18 Sickle Cell Anemia - Polymorphisms used. Mutant - HbS Wild type -HbA 19 Experimental outline - Take blood samples - Purify the dna - treat it with enzymes, spin it down to purify - Left with chromosomal DNA - Add restriction enzyme Hpa1 - involved in a polymorpsihm chang-es ite can be there or absent in certain people. - Dna was cut into millions of small pieces - Diagnosis can then be done. - Purification - run on a gel - use a probe complimentary to the sequene - Probe is radiolabelled and for a specific piece of the DNA where the polymorphism is located. - Diagnosis can then be done. - Purification - run on a gel - use a probe complimentary to the sequene Probe is radiolabelled and for a specific piece of the DNA where the - polymorphism is located. 20 - Different band sizes -changed as a result of the polymorphsim - 5 different bands 13kb long, 7.6kb long or 7kp long in different combinations. - Bands used to determine number of individuals - Dna samples from different ethnicity - Out of 73 people (samples), determined the frequency of their kbp fragment. - Not polymorphic (in whole pop) is the very left x's - The rest are the three other kb sites. AA - homozygous wildtype - 7kb and 7.6kb bands. Sometimes, its expected and not observed in the population. - - Maybe bc the same size was small or the 7kb just didn’t show up. See chart - shows the two kb lengths with the amount of individuals that are hetero, or homo for the traits. - You can inherit both polymorphisms and you will see two bands (ie lane 2). LINKAGE between 13kb and Sickle Cell disease (87% frequency) - Majority of cases (87%) ss allele is associated with 13kb fragment - Thus, the polymorphism is a reliable marker - Its not 100% and that is ideal - you want the polymorphism to be reliable but it wasn’t. - Helpful if you can identify them with certain diseases and map them. If parent is AS - inherit both alleles- recombination occurred in the child- so its 7.6 and 13 for that child. RECOMBINATION causes it to only be 87% of people with SS having sickle cell. 22 If parent is AS - inherit both alleles- recombination occurred in the child- so its 7.6 and 13 for that child. RECOMBINATION causes it to only be 87% of people with SS having sickle cell. 22 - Design a probe specific to one of the alleles but not to the other one because that site is polymorphic. - If hybridization is sensitive to the mismatch, it can be used as a diagnostic tool. - Put dna on a filter that binds to dna and add the probe to that - it hybridizes. - If the probe hybridizes with one that is wild type, the wild type individuals will show bands, the hetero will show the band but the HOMO WILL NOT SHOW THE BAND. - Difference in intensity will show the difference between homo and hetero, if the probe is VERY sensitive. 23 CYSTIC FIBROSIS - Linkage allowed cloning of the CF gene. - Linkage to another gene parozinase, linked to CF. 25 - Polymorphisms tell you about the gene - let you find the gene and find the genetic makeup - Allows you to find out how the protein performs its function. - SEE SLIDE ABOUT CF 26 - Disease caused by mutation resulting in three bp deletion. - This is at the 508 bp - With disease - lacks the AGA - Probe will not hybrid
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