Tuesday, August 3, 2010
Additional information on stuff related to forensic science
DNA Profiling
DNA profiling (also called DNA testing, DNA typing, or genetic fingerprinting) is a technique employed by forensic scientists to assist in the identification of individuals on the basis of their respective DNA profiles. DNA profiles are encrypted sets of numbers that reflect a person's DNA makeup, which can also be used as the person's identifier. It is used in, for example, parental testing and rape investigation.
Although 99.9% of human DNA sequences are the same in every person, enough of the DNA is different to distinguish one individual from another. DNA profiling uses repetitive ("repeat") sequences that are highly variable, called variable number tandem repeats (VNTR). VNTRs loci are very similar between closely related humans, but so variable that unrelated individuals are extremely unlikely to have the same VNTRs.
Polymerase Chain Reaction
The polymerase chain reaction (PCR) is a technique in molecular biology to amplify a single or few copies of a piece of DNA across several orders of magnitude, generating thousands to millions of copies of a particular DNA sequence. The method relies on thermal cycling, consisting of cycles of repeated heating and cooling of the reaction for DNA melting and enzymatic replication of the DNA. Primers (short DNA fragments) containing sequences complementary to the target region along with a DNA polymerase (after which the method is named) are key components to enable selective and repeated amplification. As PCR progresses, the DNA generated is itself used as a template for replication, setting in motion a chain reaction in which the DNA template is exponentially amplified. PCR can be extensively modified to perform a wide array of genetic manipulations.
Restriction Enzyme
A restriction enzyme (or restriction endonuclease) is an enzyme that cuts double-stranded or single stranded DNA at specific recognition nucleotide sequences known as restriction sites. Such enzymes, found in bacteria and archaea, are thought to have evolved to provide a defense mechanism against invading viruses. Inside a bacterial host, the restriction enzymes selectively cut up foreign DNA in a process called restriction; host DNA is methylated by a modification enzyme (a methylase) to protect it from the restriction enzyme’s activity. Collectively, these two processes form the restriction modification system. To cut the DNA, a restriction enzyme makes two incisions, once through each sugar-phosphate backbone (i.e. each strand) of the DNA double helix.
After isolating the first restriction enzyme, HindII, in 1970, and the subsequent discovery and characterization of numerous restriction endonucleases, the 1978 Nobel Prize for Physiology or Medicine was awarded to Daniel Nathans, Werner Arber, and Hamilton O. Smith. Their discovery led to the development of recombinant DNA technology that allowed, for example, the large scale production of human insulin for diabetics using E. coli bacteria. Over 3000 restriction enzymes have been studied in detail, and more than 600 of these are available commercially and are routinely used for DNA modification and manipulation in laboratories.
Agarose Gel Electrophoresis
Agarose gel electrophoresis is a method used in biochemistry and molecular biology to separate a mixed population of DNA and RNA fragments by length, or to separate proteins by charge. Nucleic acid molecules are separated by applying an electric field to move the negatively charged molecules through an agarose matrix. Shorter molecules move faster and migrate farther than longer ones because shorter molecules migrate more easily through the pores of the gel. This phenomenon is called sieving. Proteins are separated by charge in agarose because the pores of the gel are too large to sieve proteins.
DNA profiling (also called DNA testing, DNA typing, or genetic fingerprinting) is a technique employed by forensic scientists to assist in the identification of individuals on the basis of their respective DNA profiles. DNA profiles are encrypted sets of numbers that reflect a person's DNA makeup, which can also be used as the person's identifier. It is used in, for example, parental testing and rape investigation.
Although 99.9% of human DNA sequences are the same in every person, enough of the DNA is different to distinguish one individual from another. DNA profiling uses repetitive ("repeat") sequences that are highly variable, called variable number tandem repeats (VNTR). VNTRs loci are very similar between closely related humans, but so variable that unrelated individuals are extremely unlikely to have the same VNTRs.
Polymerase Chain Reaction
The polymerase chain reaction (PCR) is a technique in molecular biology to amplify a single or few copies of a piece of DNA across several orders of magnitude, generating thousands to millions of copies of a particular DNA sequence. The method relies on thermal cycling, consisting of cycles of repeated heating and cooling of the reaction for DNA melting and enzymatic replication of the DNA. Primers (short DNA fragments) containing sequences complementary to the target region along with a DNA polymerase (after which the method is named) are key components to enable selective and repeated amplification. As PCR progresses, the DNA generated is itself used as a template for replication, setting in motion a chain reaction in which the DNA template is exponentially amplified. PCR can be extensively modified to perform a wide array of genetic manipulations.
Restriction Enzyme
A restriction enzyme (or restriction endonuclease) is an enzyme that cuts double-stranded or single stranded DNA at specific recognition nucleotide sequences known as restriction sites. Such enzymes, found in bacteria and archaea, are thought to have evolved to provide a defense mechanism against invading viruses. Inside a bacterial host, the restriction enzymes selectively cut up foreign DNA in a process called restriction; host DNA is methylated by a modification enzyme (a methylase) to protect it from the restriction enzyme’s activity. Collectively, these two processes form the restriction modification system. To cut the DNA, a restriction enzyme makes two incisions, once through each sugar-phosphate backbone (i.e. each strand) of the DNA double helix.
After isolating the first restriction enzyme, HindII, in 1970, and the subsequent discovery and characterization of numerous restriction endonucleases, the 1978 Nobel Prize for Physiology or Medicine was awarded to Daniel Nathans, Werner Arber, and Hamilton O. Smith. Their discovery led to the development of recombinant DNA technology that allowed, for example, the large scale production of human insulin for diabetics using E. coli bacteria. Over 3000 restriction enzymes have been studied in detail, and more than 600 of these are available commercially and are routinely used for DNA modification and manipulation in laboratories.
Agarose Gel Electrophoresis
Agarose gel electrophoresis is a method used in biochemistry and molecular biology to separate a mixed population of DNA and RNA fragments by length, or to separate proteins by charge. Nucleic acid molecules are separated by applying an electric field to move the negatively charged molecules through an agarose matrix. Shorter molecules move faster and migrate farther than longer ones because shorter molecules migrate more easily through the pores of the gel. This phenomenon is called sieving. Proteins are separated by charge in agarose because the pores of the gel are too large to sieve proteins.
Script
Script
Theme song: A! is for Averregreen, she is the forensic of the awesomest team!
B! is for Bond (dun dun dun), she is the team leader of the awesomest team!
C! is for Caraway, she is secretary of the awesomest team!
D! is for Doomsday, she is assistant leader of the awesomemest team!
YEOW!!!
Scene 1 (crime scene)
(Featuring Woolly, the murderer and the neighbor’s shadows)
W: (choking sound)
M: DIE!! TAKE THAT! (punches W)
W: (groaning sound)
M: (grabs knife and stabs)
N: (witnesses the stabbing) Oh my god!
M: (slashes N)
Scene 2 (office scene)
(Featuring Bond, Caraway and Doomsday)
(B is sitting on massage chair with ‘I am the boss’ look, C is on the sofa holding a notepad and D is holding a gun and trying to find a which pose will look best in the mirror)
(phone rings)
B: Caraway! Pick up the phone now.
C: (Stops writing on notepad) Why can’t you do it?!
B: (Singsong) Watch that tone~ Remember~ Your salary~~
C: (grumble, stands up and walks towards the phone) yes boss… right away boss… (monotone) (picks up the phone and perks up) Good morning. This is Aurora Caraway from Prime Investigations Private Limited speaking. How may I assist you? (Grabs paper and pen) yup…okay. (nod) Bye and thanks for the update. (back to usual irritated self) Boss, there’s a murder down at pillow street.
B: Alright. DOOMSDAY! (D fumbles with gun) Let’s head on out. Caraway, pack the bags.
C: WHAT?! You do it!
B: If you remain helpful and smiley for the rest of the day, (singsong) I’ll double your salary~
C: (enthusiastically) Yes boss! Right away boss! (90⁰ bow)
(B & D exit. C packs the bag and follows but stumbles and falls over)
Scene 3 (crime scene)
(Featuring Bond, Caraway & Doomsday)
(everyone snaps on gloves simultaneously)
C: Ow Ow OW!
B&D: Shhhhh….
(All enter.)
D: Ahhhhhh….
(B shines a torch on the body)
B,C&D: (gasp!)
B: Hmm…a knife…& there’s a stab wound on the victim too…
D: I wonder how he died…
(Everyone stares at D)
D: (puts on big, innocent, confused eyes) what?
B (sighs) (To C & D) Go and look for clues.
C: Yes boss, right away boss!
B: uh huh…. Hmm…
D: Let’s get some samples for Averregreen.
C: Here you go boss.
(B picks up bloody knife and puts it in Ziploc bag)
B: Okay…. Caraway
C: arhhhh!!!
B: ! Time to take some pictures….. I said go look for clues!!
C: okay okay… Come on Doomsday!
D: Yup.
C: Can I use the flashlight pleaseeee!
(To D) Go get the flashlight.
(D stumbles and returns with the torch)
C: okay..okay you ready? We’ll remove that one.
C&D: OHHHH MYYY GODDDD!!!
D: What is that??? Looks like another corpse. A serial killer
C: Oh my god, oh my god.
D: Come on, let’s get some samples.
B: Doomsday, get the cotton swab. Caraway!
C: ehh sorry I forgot the bring the cotton swab…
B: how convenient.
C: Oh my god..( repeatedly)
(B takes more pictures)
B: let’s call Averregreen now.
D: yeah let’s get out
C: Okay… clear out clear out!
Scene 4 (office scene)
(Featuring Bond, Caraway & Doomsday)
C: Okay. So the guy was here…. Oh! By the way boss, I want to claim insurance on unnecessary fear and shock.
B: Sorry, didn’t hear ya.
C: I said I want to claim insurance---
B: (Cuts C off) Say that again and I’m retracting your bonus.
C: (grumbles)
D: I think we should use forensic science to solve this case. This method has become increasingly effective in modern times because of advanced technology.
B&C: okay…
B: I think we’ll give Averregreen a call
D: Yah.
C: Okay.
Scene 5 (lab scene)
(Feature Averregreen, Bond, Caraway & Doomsday)
(A is writing. B, C & D enter)
B: Hey Averergreen, we have a situation here. I need to analyze this specimen.
A: Another case? Alright, leave it to me.
B: Oh! By the way, D picked up a piece of fabric. Here you go!
A: For this case, there are 2 main pieces of evidence, the piece of fabric and the chopper that was used to murder the deceased. Hmm…there seems to be a blood stain on the fabric and possibly some skin cells too. I shall analyze it. However, I do not have enough specimen so I shall make use of the polymerase chain reaction. The polymerase chain reaction is a technique in molecular biology to amplify a single or few copies of a piece of DNA across several orders of magnitude, generating thousands to millions of copies of a particular DNA sequence. This process takes 2 hours.
Scene 6 (lab scene)
(Featuring Averregreen, Bond, Caraway & Doomday)
C & D: Hey Averergreen, we’ve come to collect the specimen.
(B strolls in)
C & D: Oh hi boss.
B: Hey, any progress so far?
A: Yes. For this case, I have used agarose gel electrophoresis. As you can see here. Agarose gel electrophoresis is a method used in biochemistry and molecular biology to separate a mixed population of DNA and RNA fragments by length or to separate proteins by charge.
C: There seems to be a match with a person called Akila Lede Sheepa.
B: That’s a weird name…do we know his whereabouts?
A: Hang on…let’s see… Well, he lives at 999 Ima Balla Lina Street.
(All laugh at the atrocity of the street name)
D: Let’s go!
C: We’ll go and arrest him!
(Bond, Caraway & Doomsday leave)
A: As one can see from the skit presented, forensic science is highly effective in solving cases.
(Camera focuses one last time)
A, B, C & D: (Bow) Thank you! (Jump into the air)
Synopsis of Video.
The skit presented is about 4 members of the CSI team, Barbie Averregreen, Jane Bond, Aurora Caraway, and Alex Doomsday. Averegreen is the forensic scientist, Bond is the team leader, Caraway is the assistant, and Doomsday is the assistant leader. They are asked to investigate a murder that occurred. They find out that the murderer is actually a serial killer that killed two people. They manage to gather some specimens and bring it to Averregreen for testing. Averregreen used DNA profiling to solve the case. She used the agarose gel to look for DNA patterns. In the end, they solve the case and figure out who the murderer is!
WARNING.
WARNING
This video is only to be used for viewing purposes only. Reproduction of this video is not allowed unless there is permission obtained from the producers. In addition, this video is completely based on a fictional storyline and characters. Similarity to any situation or anyone is not intended. Thank you and enjoy the presentation.
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