Essay
Unit 13 Assignment B - DNA Amplification
- Module
- Unit 13 - Forensic Genetics
- Institution
- PEARSON (PEARSON)
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Unit 13Assignment B
DNA Extraction and Amplification
DNA extraction and amplification is so vital for the helping of forensic cases, it allows DNA to
be replicated and photocopies, to provide longer samples for forensic analysis. It can be
used for a variety of reasons, whether it’s for biomedical purposes, historical purposes or
forensic/cold case analysis purposes. Extraction is vital for isolating specific DNA samples in
order to be amplified by methods such as PCR (polymerase chain reaction), this is the
experiment we did in order to amplify DNA. Without PCR/amplification, many cases would
go unsolved due to the fact that there isn’t enough DNA to confirm a suspect. PCR allows for
that DNA to be further analysed and compared in databases to find a match, making it vital
for solving cases.
Why does DNA need to be extracted and amplified?
It is necessary that DNA is extracted and amplified for the reasons stated above. Without
DNA extraction and amplification, there simply may not be enough DNA for an adequate
analysis. If a lab only had a singular strand of DNA, that would hinder any investigation/work
that needs to be done as you cannot read off of a singular strand of DNA. DNA extraction is
essential for being able to analyse any biological evidence such as saliva, blood or hair and
allows for the identification of individuals whether they be victims or suspects of a crime. It
allows access for genetic information and analysis. Amplification allows for degraded DNA to
be analysed, or specific parts of DNA so profiles can be created.
Kiwi Fruit and Saliva DNA Extraction
Materials needed:
● Kiwi fruit
● A knife and chopping board
● Fork/spoon
● Sieve
● Lysing Solution
● Chilled ethanol
● 60 degrees Celsius water bath
● Beaker
Method:
1. Peel the kiwi fruit with the knife. And then chop the kiwi
fruit into quarters.
2. Use a singular quarter and mash it up into a paste, this
can be using a fork/spoon and can also be done on the
chopping board.
3. Get a beaker (250ml) and place the paste inside the
beaker.
4. Grab your lysing solution, and place it in the beaker after
measuring it out.
Figure 1 - Kiwi Fruit DNA
, 5. Then, using the sieve, transfer the kiwi and lysing solution to another separate
beaker. Leaving what is left of the paste behind.
6. After this, get the chilled ethanol. Pour it gently down the side of the beaker to ensure
the DNA is separated. This should appear as a clear layer on top of the kiwi liquid.
7. The DNA should be visible at the top of the beaker. This is the DNA mitochondria
that has been extracted.
Materials needed:
● 15ml tube containing 3 ml of water
● 2 ml of lysis buffer
● Contact lens cleaner (protease)
Method:
1. Label the 15ml tube containing 3ml of water as yours.
2. Chew the inside of your mouth for 30 seconds in order to
produce saliva.
3. Swirl the 3ml of water inside your mouth for 30 seconds.
4. Spit the water back into the 15ml tube.
5. Add 2ml of lysis buffer.
6. Place the cap on the tube and invert 5 times.
7. Add 4/5 drops of contact lens solution into the tube.
8. Invert the tube a few times. This should have extracted
your mitochondrial DNA.
Figure 2 - Saliva DNA
9. Leave the tube within a water bath and upright undisturbed
for 5 minutes to allow for extraction.
From these experiments we can visually observe the DNA through the presence of the white
string-like material, meaning our extraction was successful. Prior to this experiment, this
wasn’t visible, and only became so after ethanol was added for the kiwi fruit and contact lens
solution for the saliva. To improve this experiment, you could try to put these DNA samples
into an electrophoresis machine in order to analyse them.
Preparing the Plasmids for DNA Extraction
This part of the experiment allows for the plasmid pARA-A, to be inserted into bacterial cells.
It also allows for another plasmid pARA-R, to grow under different conditions to the pARA-A.
Risk assessment:
● A 42 degrees Celsius water bath could cause burns or electrocution so ensure that
the water bath is plugged in correctly and checked for electrical faults prior to use.
● Reagents include bacterial plasmids so ensure that appropriate PPE is worn (gloves,
goggles and lab coats) to avoid illness.
Materials:
● Micropipette (both 2-20 and 50-200 microlitres)
● Pipette tips
● 1.5mL empty microfuge tubes (x2)
● Floating tube racks (x2)
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