Techniques for DNA testing Restriction Enzymes RESTRICTION enzymes
- Slides: 7
Techniques for DNA testing
Restriction Enzymes � RESTRICTION enzymes are used to cut DNA into FRAGMENTS that are many different LENGTHS and exhibit POLYMORPHISM which is many shapes ◦ DNA molecule too long & complex; must characterize into pieces ◦ Restriction enzymes cut the DNA into smaller pieces �Recognizes specific sequences and cuts at a specific point �Ex) Eco. Ri will cut when they see sequence GAATTC �Cut between G & A
RFLP � Once DNA is cut; fragments are separated through electrophoresis � Probe (segment of DNA with a known sequence of bases) will be added to adhere to specific fragments ◦ Four Main procedures �Isolate DNA from cell �Cut with a restriction enzyme �Sort segments �Analysis Printing
Electrophoresis � Procedure separates DNA fragments according to size � DNA is negatively charged � Negative end of DNA will attract to positive end of electrodes � Shorter fragments travel farther � Can be used to match fragments from samples
PCR (Polymerase Chain Reaction) � Uses very small DNA sample & makes millions of copies � Require 50 times less DNA than RFLP � Makes copies of DNA over and over using the base pairs and the fact they can break the hydrogen bonds � Three Steps ◦ Separate DNA strands ◦ Add a primer to add complimentary base pairs ◦ Make a new strand � When DNA is amplified, characteristics can be shown by adding genetic markers
STR (Short Tandem Repeats) � Takes Least amount of time, Even smaller fragments, and it is more exclusionary � Locations on chromosomes that repeat a specific sequence � Can be amplified by using PCR � Can create a DNA profile to help catch a suspect
Review � What is the function of a restriction enzyme? � What do the letters RFLP stand for? � What is electrophoresis and how does it work? � Why is STR better to use than PCR or RFLP?
