QuestionsWhat is the genotype of each of the DNA samples? Whose DNA is left at the crime scene?         Lane of gelDNA sampleGenotype1Allele LadderN/A2Crime Scene DNA7-3 (allele 7 + allele 3)3Suspect A10-3 (allele 10 + allele 3)4Suspect B5-2 (allele 5 + allele 2)5Suspect C7-3 (allele 7 + allele 3)6Suspect D10-2 (allele 10 + allele 2)        Suspect C DNA is left at the crime scene. Suspect C DNA is the same as the Crime scene DNA by matching them. Each of their DNA had two fragments that each migrated displaying that they were the same size.What components do you need to perform a PCR and what is the function of each component? What is contained in MMP?We need DNA template, DNA polymerase, primers, Nucleotides (dNTPs or deoxynucleotide triphosphates) and reaction buffer. DNA template: sample DNA which contains target sequence.DNA polymerase: An enzyme which new strands of DNA complementary to the target sequence such as Taq polymerase. Taq polymerase is a thermostable enzyme that will not denature at high temperature.Primers: short oligonucleotides of DNA, vary from 8 to 60 base pairs in length. Sequences can be randomized if the goal is for general genomic studies. For amplifying individual sections of the DNA in the genome, primers of specific sequences will be used instead. Nucleotides: building blocks for DNA replication Reaction buffer: Provides a stable pH.Master mix primer(MMP) contains Taq DNA polymerase( dATP, dGTP, dCTP, dTTP), dNTPs, salt buffer, MgCl2 and additives in a buffer at a favourable concentration which is optimized for PCR. A salt buffer will maintain a neutral pH for the PCR reaction and magnesium chloride is a cofactor needed by DNA polymerase. Why do you need to run a PCR before gel electrophoresis?DNA is amplified as there is little amount of the sample available, hence, PCR needs to be run through. This procedure can be applied for anything from the hair follicle, fingernail, teeth, saliva, skin cells and other biological materials. PCR works by replicating the DNA to more similar copies to perform a forensics test. Explain in your own words what is the difference between allele, locus and loci? The difference in an allele, locus and loci is that an allele is a variation of a gene found in the chromosome whereas a locus is the location of the particular gene found in the chromosome and a loci is basically a plural form of locus. Explain why you should load the DNA samples at the cathode end of the electrophoresis chamber.For the separation of the DNA fragments, gel electrophoresis is used according to their charge and size. DNA samples are negatively charged. It will be placed at the cathode end of the chamber. By placing at the cathode end, the DNA will move towards the anode end which is also the positive electrode of the electrophoresis chamber. There is the same amount of charge per mass for all DNA samples. This will allow small DNA samples to move at a faster speed through the gel compared to the large ones.  Explain the principle of gel electrophoresis in separating DNA fragments.In order to separate the DNA fragments, gel electrophoresis is used. After creating wells by using a comb and by solidifying the gel, the DNA samples are added into the wells via a pipette. They are seen as stains on the gel. The electric current is then run through at 100 volts from the negatively charged DNA to the positively charged DNA. Once the gel has been run through thoroughly, it can be viewed under ultraviolet light after staining and destaining. The smaller fragments include less mass of DNA, as a result they would absorb less of the dye and hence, when viewed under ultraviolet light, there would be less fluoresce. Furthermore, the DNA ‘ladder’ also known as the DNA fragments are located at the extreme right and are used to identify the unknown fragments and their sizes.           ConclusionOverall, it was a rather successful and enriching experiment for us. We were able to get our desired destaining results in a rather short period. We were able to accurately deduce the correct suspect which is suspect C through the destained gel. Through this experiment, we were able to learn a real world application of PCR and gel electrophoresis.


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