University Biology: Agarose Gel Electrophoresis and Forensics

This assignment solution focuses on agarose gel electrophoresis, a technique used to separate DNA fragments based on size. The document analyzes two case studies: a crime scene investigation at Paul's Pierogi Palace and a paternity dispute. It explains how DNA evidence, obtained from sources like the "Terrible Towel" and potential suspects, can be used to identify individuals and solve crimes. The solution covers the principles of PCR, DNA stability, and the complementary base pairing of DNA strands. It also addresses the limitations of DNA evidence, such as contamination and degradation, and how these factors affect the reliability of results. The assignment demonstrates the application of electrophoresis in forensic science, highlighting how the banding patterns of DNA fragments can be used to match suspects to crime scenes and determine biological relationships.

Running Head: AGAROSE GEL ELECTROPHORESIS
AGAROSE GEL ELECTROPHORESIS
Name of the Student
Name of the University
Authors Note

1AGAROSE GEL ELECTROPHORESIS
Solution 1:
Suspect 2 is likely the burglar of Paul’s Pierogi Palace. The DNA profile of the suspected
exhibits the same electrophoresis banding pattern with that of the evidence DNA. The bands are
identical. The pores of the gel separate the molecules of DNA according to size which forms
distinct bands in the gel. The bands are formed according to the size of the DNA fragments.
Solution 2:
The DNA from partially eaten pierogis cannot be used as an evidence to catch the suspect. This
is because the majority of DNA in the saliva present on the half eaten food contains white blood
cells and bacteria. DNA when extracted from saliva might contain bacterial DNA as our mouth is
rich in bacterial micro flora for digestion of food (Yao et al. 2016).
Solution 3:
The microscopic amount of DNA can be used to help solve a crime. The tiny amount of DNA
can be amplified using the techniques of PCR. PCR stands for Polymerase Chain Reaction. It is a
molecular biology process that generates many copies of a specific DNA segment. It a process of
thermal cycling where the DNA is enzymatically melted, primers, nucleotides and polymerase
are added artificially to generate more number of complementary DNA strands (Ahrberg, Manz
and Chung 2016).
Solution 4:
Father 1 is the biological father of the child. The DNA profile of the Father 1 exhibits the same
electrophoresis banding pattern with that of the child DNA. The bands are identical. The pores of

2AGAROSE GEL ELECTROPHORESIS
the gel separate the molecules of DNA according to size which forms distinct bands in the gel.
The bands are formed according to the size of the DNA fragments.
Solution 5:
The DNA from Terrible Towel can be used as a strong evidence to identify the suspect. The
DNA bands from the crime scene gel electrophoresis pattern was identical with that of the DNA
banding pattern of the suspect 1. Since the DNA bands were identical in case of Terrible Towel
gel electrophoresis, this DNA evidence can be a strong area to identify the suspect.
Solution 6:
In gel electrophoresis, some DNA fragments move faster and farther as compared to other DNA
fragments in agarose gel. This happens because some DNA fragments are smaller in size which
can move faster and farther in the gel in response to the electric current as compared to larger
fragments. Since the DNA fragments are smaller in size, they face minimum resistance in the
pores of agarose gel and can migrate farther (Nsofor 2016).
Solution 7:
DNA molecule is very stable. Mutations in the nitrogen bases of DNA is very rare. Each DNA
strand contains unique sequence or code of genetic information. The nitrogen bases of DNA
adenine, guanine, thymine and cytosine are highly stable. The double stranded DNA is also
highly stable. Adenine forms double hydrogen bonds with thymine and guanine forms triple
hydrogen bonds with cytosine.
Solution 8:
The complementary base sequence of GCATG is CGTAC.

3AGAROSE GEL ELECTROPHORESIS
Solution 9:
DNA directs the process of protein synthesis through the process of transcription and translation.
Transcription is a technique in which the genetic information contained in the DNA is copied
into a molecule of mRNA. This step is carried out by the enzyme RNA polymerase. The mRNA
is translated into proteins. The genetic information of the DNA gets converted into proteins
through the Central Dogma of Molecular Biology (Marshall 2017).
Solution 10:
The DNA fragment of 200 bp moves faster and farther during gel electrophoresis. This happens
because DNA fragments that are smaller in size can move faster and farther in the gel in
response to the electric current as compared to larger fragments. Since the DNA fragments are
smaller in size, they face minimum resistance in the pores of agarose gel and can migrate farther.

4AGAROSE GEL ELECTROPHORESIS
References
Ahrberg, C.D., Manz, A. and Chung, B.G., 2016. Polymerase chain reaction in microfluidic
devices. Lab on a Chip, 16(20), pp.3866-3884.
Marshall, P.A., 2017. A hands-on activity to demonstrate the central dogma of molecular biology
via a simulated VDJ recombination activity. Journal of microbiology & biology
education, 18(2).
Nsofor, C.A., 2016. Pulsed-field gel electrophoresis (PFGE): principles and applications in
molecular epidemiology: a review. Int J Curr Res Med Sci, 2(2), pp.38-51.
Yao, W., Mei, C., Nan, X. and Hui, L., 2016. Evaluation and comparison of in vitro degradation
kinetics of DNA in serum, urine and saliva: a qualitative study. Gene, 590(1), pp.142-148.