What is DNA Profiling?A technique used to identify individual by encrypting setsof numbers that reflect a person’s DNA makeup. (Oftenused in parental testing and criminal investigation)
Assessment Statement related to DNA Profiling4.4.3 State that gel electrophoresis of DNA is used inDNA profiling.4.4.4 Describe the application of DNA profiling todetermine paternity and also in forensicinvestigations.4.4.5 Analyse DNA profiles to draw conclusions aboutpaternity or forensic investigations.
How does gel electrophoresis work?Gel electrophoresis is used to separate DNA (or othermolecules) by their size and charge. The DNA fragmentsmove in an electric field. The negatively charged DNA allmoves towards the positive electrode. Small pieces movefarther than large pieces.
Procedure of DNA Profiling1. DNA samples are taken and amplified with PCR2. Restriction enzymes cut DNA into fragments at specific base sequencesin each sample3. a fluorenscent marker blinds to a triplet in the DNA fragments, so thatresults can be seen4. Samples are added to a gel electrpphoresis chamber. Electric current ispassed through, pushing the fragments along5. Heavier fragments stay closer to the origin and smaller fragments gofurther6. a banding pattern shows up for each DNA sample and can be compared
What is PCR (polymerase chain reaction) used for?-copy and amplify tiny quantities of DNA. Very useful ifyou only have a small sample of DNA (like from a bloodsample from a patient or a crime scene) and you need lotsof DNA to do DNA profiling.
Which electrode (positive ornegative) will DNA travel towards in gel electrophoresis? Why?positive electrode; DNA is negatively charged (think of allof those phosphate groups!). Note that if the electrodes arenot labelled in a gel
4.4.5 Analyse DNA profiles todraw conclusions about paternity or forensic investigations.
From Senior biology BookMicrosatellites(short tandem repeats): repeatingsequences(2-6 base pairs)Because noncoding nucleotide sequences repeatthroughout the genome, the finding of repeatingsequences(DNA profiling) is possible.
4.4.4 Describe the application of DNA profiling to determine paternity and also in forensic investigations.Organisms have short sequences of bases which are repeated many times.These are called satellite DNA. These repeated sequences vary in lengthfrom person to person. The DNA is copied using PCRand then cut up intosmall fragments using restriction enzymes. Gel electrophoresis separatesfragmented pieces of DNA according to their size and charge. This gives apattern of bands on a gel which is unlikely to be the same for twoindividuals. This is called DNA profiling. DNA profiling can be used todetermine paternity and also in forensic investigations to get evidence tobe used in a court case for example.