Question

3. PCR analysis practice One 3) If you collect samples from crime scene and extract DNA out of each sample. Describe the technologies used to get the below results. 4) Identify which suspect is at the crime scene 5) Among suspect 1-3, who is homozygous for the tested locus and who is heterozygous? DNA from crime scene DNA ladder suspect DNA #1 #2 #3 500 bp 400 bp 300 bp 200 bp 100 bp — I 4. PCR Practice two 1) What technologies could be used to test for biological fathers? 2) Among human DNA sequence, which parts of the DNA sequence could be used for DNA fingerprinting? 3) is the guy tested below the biological father of the child?

Answer 1

PCR practice one

3. Answer and Explanation:

The technologies used here is PCR (Polymerase chain reaction) and STR analysis. STR is nothing but short tandem repeats of nucleotides at specific locus. The number of repeats will differ from individual to individual. Increasing the number of loci will increase the discrimination. For every individual there will be one (homozygous) or two bands (heterozygous) for each loci.

The target STRs will be amplified using the polymerase chain reaction to make millions of copies using STR specific primers and then loaded on to the agarose gel. After gel electrophoresis, the suspect samples will be compared with the crime scene to find the suspect at the crime scene.

4. Suspect 3 was the one at crime scene. By comparing the size of the bands with the help of the DNA marker, it is observed that the size of the crime scene DNA for the particular STR is 200 bp and it is matching with the suspect 3.

5. Suspect 3 is homozygous for the tested loci and suspect 1 and 2 are heterozygous because the suspect 3 has only one band which shows it is homozygous and other two have two bands which shows it came from two alleles (heterozygous - allele 1 and allele 2).