Activity 1.1.5 - DNA Evidence Conclusions

Identify all of the potential sources of DNA

-Bone -Hair -Preserved Body Parts -Clothing and Fibers -Saliva and Body Fluids

What is a restriction enzyme?

Restriction enzymes are enzymes used to cut within a DNA molecule.

Identify the enzyme that is used during the PCR process .What is the main reason that enzyme is used in the process?

Taq polymera. Taq polymera completes the replication of DNA strands.

Which DNA bases are classified as pyrimidines?

Cytosine, Uracil, & Thymine

Which DNA bases are classified as purines?

Guanine & Adenine

What are some possible sources of DNA from the scene where Anna Garcia's body was found? Explain.

Hair and fingerprints. These are easy DNA sources to leave behind at a crime death.

Distinguish between pyrimidines and purines. What makes them different. Be sure to include any structural differences.

Pyrimidines bases are Cytosine, thymine, and uracil. Adenine and guanine are the two purine bases. Pyrimidine has one ring and purine has two rings. Purine has a pyrimidine ring and an imidazole ring. Adenine and guanine are the purine derivative present in nucleic acids whereas cytosine, uracil and thymine are the pyrimidine derivatives present in the nucleic acids. Purines have more intermolecular interactions than pyrimidines. Melting points and boiling points of purines are much higher compared to pyrimidines.

Briefly describe the process of PCR. Be sure to include all of the steps/stages of the process.

The DNA fragment to be copied is mixed with a pool of free DNA nucleotides and heat resistant DNA polymerase enzyme (Taq polymerase which does not denature at high temperatures). Two primers are made in the laboratory which have matching base pairs to the 3' ends of the DNA fragment and are added to the mixture. Then the mixture is heated to 93 degrees, then 55 degrees, then back to 72 degrees. This is one complete cycle (Source: Polymerase chain reaction (PCR) Flashcards | Quizlet)

What are some challenges in extracting DNA from samples related to an active investigation?

There is a possibility that DNA won't match up with suspects that are in a active investigation case.

DNA has two strands. If the sequence of nucleotides of one strand was known, is it possible to use that information to determine the sequence of the second strand? Explain your reasoning for your response using an example DNA sequence.

Yes, You can figure out the second strand by pairing the bases (A-T,C-G). Once you pair the bases you will have a new strand of DNA.

Can you be framed by your own DNA? How might an individual's own cells lead to false verdicts of guilt? In your explanation, provide one scenario in which this might occur.

Yes, you can. DNA can be easily extracted from your body. DNA cells can find their way to a crime scene where we had never physically been to. DNA cells are mobile and easy to extracted while people are moving throughout the day. For example, a hair strand falling from your hair. Someone finds it and puts it at the scene of a murder that just occurred.