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DNA Evidence. How can DNA be used to solve Crimes?. Objective : Describe how DNA can be analyzed and used as evidence. Do Now : Why is DNA considered circumstantial evidence? In groups of 5 or less, work together on the DNA questions. Write all names and answers on loose-leaf paper. Hand in.

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dna evidence

DNA Evidence

How can DNA be used to solve Crimes?

objective describe how dna can be analyzed and used as evidence
Objective: Describe how DNA can be analyzed and used as evidence.

Do Now: Why is DNA considered circumstantial evidence?

In groups of 5 or less, work together on the DNA questions. Write all names and answers on loose-leaf paper. Hand in.

Closure: At a crime scene, list at least 3 places investigators should look for DNA evidence.

slide3
Objectives: Describe what DNA is and identify the different types of DNA

Do Now: Where can DNA come from? Brainstorm all evidence that may have DNA

what is dna
Objectives: Describe what DNA is and identify the different types of DNAWhat is DNA?

DNA contains genetic information.

Found on chromosomes located in the nucleus of our cells**

Individual Evidence

slide5
Objectives: Describe how DNA can be analyzed and used as evidence. Explain the importance of CODIS in forensic science.

CYTOSINE

THYMINE

GUANINE

ADENINE

  • Made up of base pairs: (think of a bar code)
    • A – T
    • C – G
  • The order of the base pairs determines the genetic code
human dna
Objectives: Describe how DNA can be analyzed and used as evidence. Explain the importance of CODIS in forensic science.Human DNA
  • 50% of a person’s DNA comes from each parent
    • 23 pairs (46 chromosomes) in nucleus of most cells*
    • 1 chromosome in each pair is inherited from mother and other from the father
  • Every person has a different DNA

sequence expect identical twins.

**How can we distinguish between

identical twins apart?

types of human dna
Objectives: Describe the different types of DNA can be analyzed and used as evidence. Types of Human DNA
  • NUCLEAR DNA: found in chromosomes
    • Used for DNA Fingerprinting
    • Unique to individual
  • MITOCHONDRIAL DNA: Found in mitochondria
    • Inherited from mother
    • Not unique
    • Example: bone, hair shaft
why use mdna
Objectives: Describe how DNA can be analyzed and used as evidence. Why use mDNA?

More stable over time/conditions*

Can get more DNA if sample is limited

Can get DNA from a highly degraded source

how is dna used
Objectives: Describe how DNA can be analyzed and used as evidence. How is DNA used?

Identify a victim

Link or exclude suspect to crime scene/evidence

Link multiple crime scenes

Establish Maternity/Paternity

what factors affect dna evidence
Objectives: Describe how DNA can be analyzed and used as evidence. What Factors Affect DNA evidence

Heat, sunlight, moisture, bacteria, and mold (this was a major issue in the O.J. Simpson Case)

Not all DNA evidence will result in a usable DNA profile.

DNA testing cannot identify when the suspect was at the crime scene or for how long.

what is codis
Objectives: Describe how DNA can be analyzed and used as evidence. Explain the importance of CODIS in forensic science.What is CODIS?

Electronic database of DNA profiles that can identify suspects.

DNA profiles from individuals convicted of certain crimes, such as rape, murder, and child abuse, are entered into CODIS and help identify possible suspects when no prior suspect existed.

introduction to dna fingerprinting
Objectives: Describe how DNA can be analyzed and used as evidence. Explain the importance of CODIS in forensic science.Introduction to DNA Fingerprinting

http://www.youtube.com/watch?v=RLpalVirlTk#t=322

slide14
Watch the video and then answer the questions.

Video Link: http://videos.howstuffworks.com/tlc/29325-understanding-using-genes-to-help-solve-crimes-video.htm

1. When did DNA start to be an important tool in forensics?A. 1880s B. 1960s C. 1980s

2. What type of evidence does the FBI consider its most powerful tool?A. Fingerprints B. Blood C. DNA

3. What program is used to match DNA samples to possible contributors?A. CODIS B. AFIS C. DNA Code

4. What is it called when the program makes a match?A. Hot Hit B. Cold Hit C. Dead Hit

5. How many criminals have been convicted based on this software?A. 300 B. 900 C. 1,500

slide15
Objectives: Describe the role of DNA in the O.J. Simpson case

Do Now: What are some factors that degrade (affect) DNA?

slide16
The answers are …

1. When did DNA start to be an important tool in forensics?A. 1880s B. 1960s C. 1980s

2. What type of evidence does the FBI consider its most powerful tool?A. Fingerprints B. Blood C. DNA

3. What program is used to match DNA samples to possible contributors?A. CODIS B. AFIS C. DNA Code

4. What is it called when the program makes a match?A. Hot Hit B. Cold Hit C. Dead Hit

5. How many criminals have been convicted based on this software?A. 300 B. 900 C. 1,500

slide17
Objectives: Describe the role of DNA in the O.J. Simpson case

http://law2.umkc.edu/faculty/projects/ftrials/Simpson/Dna.htm

Complete DNA and the O.J. Simpson case study

Closure: The DNA found at the scene only shows OJ was present for the crime. What other evidence could they/did they find to try to link him as their major suspect?

2 main types of dna testing
Objectives: Describe how a DNA fingerprint is performed2 Main Types of DNA Testing
  • RFLP: * analyzes variable lengths of DNA cut by restriction enzymes.
      • requires large amounts of DNA and no degradation

RFLP: Restriction Fragment Length Polymorphism.

slide20
Objectives: Describe how a DNA fingerprint is performed

Restriction enzymes: cut DNA at specific base sequences resulting in variable lengths of DNA

slide21
Objectives: Describe how a DNA fingerprint is performed

Gel Electrophoresis: Method of separating molecules of DNA within an electric field based on the size and charge of DNA fragments

objectives describe how a dna fingerprint is performed
Objectives: Describe how a DNA fingerprint is performed

http://www.dnalc.org/resources/animations/gelelectrophoresis.html

More probes taken, the better the match probability will be.

Denim blue jeans actually interfere with the restriction enzymes!

slide24
Objectives: Describe how a DNA fingerprint is performed

How are gel electrophoresis results analyzed?

slide26
Objectives: Describe how a DNA fingerprint is performed
  • Complete the following activities:
    • Who are the parents
    • Which man is the father
  • Closure: If everyone gave their DNA to CODIS every substantial crime could be run through the CODIS program to produce cold hits. This would solve more crimes faster. Would you agree to giving your DNA to the government to run a program like that?
slide27
Objectives: Describe how a DNA fingerprint is performed

Do Now: What does a restriction enzyme do?

slide28
Objectives: Describe how a DNA fingerprint is performed

2nd Main type of DNA testing:

PCR: (Polymerase Chain Reactions) specific sequences of DNA that have high variability (differences) are copied millions of times

  • Less DNA needed and can be partially degraded
slide29
Objectives: Describe how a DNA fingerprint is performed

Newest type of DNA testing:

STR: Evaluates specific short repeating regions (loci) within nuclear DNA

FBI uses 13 standard specific STR regions for CODIS

slide30
Person A

Forensic sample

STR

STR

G-G-C-C-X-X-X-G-G-C-C-X-X..

G-G-G-C-C-X-X-G-G-C-C-X-X…..

PCR amplify

STR region

C-C-X-X-G-G

C-C-X-X-X-G-G

well

well

Gel

electrophoresis

For 1 STR sequence at 1 locus

slide32
Objectives: Describe how a DNA fingerprint is performed

STR match probabilities are 1 in a quintillion (1x1018) or more

slide33
Objectives: Describe how a DNA fingerprint is performed
  • Complete “The break in” activity and concepts of biotechnology reading. And hand in.
  • Closure: Name three different reasons why a DNA profile may be needed to identify a person.
slide34
Objectives: Construct a gel electrophoresis simulation and determine who committed the crime
  • Do Now: What is an advantage to PCR over RFLP?
slide35
Objectives: Construct a gel electrophoresis simulation and determine who committed the crime
  • Start the individual DNA Fingerprinting Lab and hand in.
  • Closure: If we only have 4 bases (AGCT) that our DNA is made up of, how can everyone's DNA be completely different? Hand in your closure/do now sheet.
objectives construct a gel electrophoresis simulation and determine who committed the crime
Objectives: Construct a gel electrophoresis simulation and determine who committed the crime

Do Now: Can any two people have the same DNA? Can any have the same mDNA?

Finish the individual DNA Fingerprinting Lab and hand in.

Closure: Do other animals have DNA?

objectives construct a gel electrophoresis simulation and determine who committed the crime1
Objectives: Construct a gel electrophoresis simulation and determine who committed the crime

Do Now: There’s a copy of our entire DNA sequence in every cell of our body with one exception: red blood cells. But our sex cells only have ______ of our DNA.

Finish the individual DNA Fingerprinting Lab and hand in. (20min)

objectives construct a gel electrophoresis simulation and determine who committed the crime2
Objectives: Construct a gel electrophoresis simulation and determine who committed the crime

Complete the DNA profile review sheet. Hand it in.

Closure: Besides determining suspects or paternity, what else can DNA be used for?

objectives describe how a dna fingerprint is performed1
Objectives: Describe how a DNA fingerprint is performed

Do Now: Why does the DNA travel to the bottom of the gel electrophoresis chamber?

Watch the video and take notes on your handout. This will be due tomorrow when we finish the video.

Closure: What DNA did the suspect leave behind?

objectives construct a gel electrophoresis simulation and determine who committed the crime3
Objectives: Construct a gel electrophoresis simulation and determine who committed the crime

Do Now: What are the base pairs I DNA and how do they match up?

Start the group DNA profile lab and hand in.

Closure: One chromosome can have as little as 50 million base pairs or as much as 250 million base pairs. How many chromosomes do we have?

objectives construct a gel electrophoresis simulation and determine who committed the crime4
Objectives: Construct a gel electrophoresis simulation and determine who committed the crime

Do Now: What does the gel electrophoresis do?

Complete the group DNA profile lab and hand in.

Closure: Check your grades. Write down what you are missing.

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