50. Alcohol Lecture51. Drug Lab Part 252. Erin Brokovich53. What is DNA?54. DNA Structure – notes, model, ?s55. DNA Lab 56. Forensic DNA Analysis57. DNA Fingerprints – notes, picture, activity58. Collecting and Preserving DNA Evidence 59. The Long and Short of DNA – highlighted article60. Forensic Tools Crossword61. Ballistics Lecture62. Firearms 63. Bullet Markings

MAY ROOT WORD QUIZ TODAY!

#53 What is DNA? Pages 361 – 366 & Internet • Thousands of genes are arranged on…

• The gene is the…• Genes instruct our body cells to…• 1950s – Watson and Crick…• DNA is a polymer which is…• DNA is made up of repeating units of…• DNA directs the production of…• What is the human genome?• Research: What is the Innocence Project?• Research: Significance of Maryland vs. King

with regards to DNA evidence.

#54 DNA STRUCTURE• DNA is found in all cells (nucleus)• Double helix• Made up of nucleotides– 3 parts: • phosphate• Deoxyribose• Differing nitrogen bases AT and CG (base pairing)inside of DNA molecule (the rungs)

• Antiparallel• Rosalind Franklin• Watson and Crick – won Nobel Prize for

discovery of DNA structure

Answers to the Pre-Lab• 1. deoxyribose nucleic acid• 2. True• 3. brought out of the solution so

it can be seen• 4. lysate: pink liquid containing

strawberry DNA• 5. interface: where DNA meets

liquid during the precipitation process

• 6. color: whiteshape: double helixsolubility: dissolves in

water, not alcoholcharge: negativepH: determine this using pH

paper

1. How was DNA evidence used to prove that Dr. Sam Sheppard did not murder his wife?

2. Why wasn't this evidence used when the case first went to court?

3. Why do you think the DQA1 test was chosen for DNA analysis in this case, instead of another, more powerful genetic test?

4. If the blood trail left at the murder scene wasn't Marilyn's or Sam's, whose blood might it have been?

5. If you were a juror on this trial, would you be convinced by the DNA evidence?

http://www.pbs.org/wgbh/nova/education/body/forensic-dna-analysis.html#56. Forensic DNA Analysis

1. How was DNA evidence used to prove that Dr. Sam Sheppard did not murder his wife?

2. Why wasn't this evidence used when the case first went to court?

3. Why do you think the DQA1 test was chosen for DNA analysis in this case, instead of another, more powerful genetic test?

4. If the blood trail left at the murder scene wasn't Marilyn's or Sam's, whose blood might it have been?

5. If you were a juror on this trial, would you be convinced by the DNA evidence?

http://www.pbs.org/wgbh/nova/education/body/forensic-dna-analysis.html#56. Forensic DNA Analysis

The Candy Culprit

http://www.pbs.org/wgbh/nova/education/body/create-dna-fingerprint.html

Making a DNA Fingerprint• 1) Collect cell sample

• 2) Extract DNA from cells

• 3) Cut DNA into piecesRestriction enzymes: work like scissors to cut DNA at certain locations

• 4) Electrophoresis occurs~Gel: acts as strainer, allows DNA to move through it, small pieces go farther~Electrophoresis: the process of moving molecules with an electrical current~DNA is negatively charged so it will move to the + end of the machine

• 5) The pattern in the gel is transferred to a nylon membrane: Southern Blotting

• 6)Adding a radioactive DNA probe will bind to specific sequences of DNA (stain)

• 7) X-ray film is used to detect radioactive pattern

#58. Collecting and Preserving DNA Evidence

• Read pages 390 – 395 and take notes on:– How many cells are needed to obtain an STR

profile– Low copy number– Epithelial cells– Table 13-2 (know cigarette, hat/mask,

envelope, can, fingernail, sheet)– First step in collecting evidence– Packaging and storage of evidence– Evidence in soil– Contamination– Steps to minimize contamination

#58. Collecting and Preserving DNA Evidence

• Read pages 390 – 395 and take notes on:– How many cells are needed to obtain an STR

profile– Low copy number– Epithelial cells– Table 13-2 (know cigarette, hat/mask,

envelope, can, fingernail, sheet)– First step in collecting evidence– Packaging and storage of evidence– Evidence in soil– Contamination– Steps to minimize contamination

Ballistics• Ballistics – the study of projectiles (bullets)

and firearms• Firearm – a weapn capable of firing a

projectile using a confined explosive as a propellant.

• Ballistic evidence helps explain:– Type of firearm–Caliber of bullet–Number of bullets fired–Where the shooter was located–Whether a weapon was fired recently– If a firearm was used in previous crimes

History of firearms• Chinese invented gunpowder: fireworks• 14th Century Europe: directed gunpowder

down cylinder to fire a projectile• Matchlock weapons: used wick to carry

flame to gunpowder• 16th Century: Wheelock: used a wheel to ignite spark

• 17th Century: Flintlock: uses sparks from a chip or flint; allowed to fire in wet weather

• Muzzle-loading: user puts the gunpowder and projectile down the barrel

• 19th Century: Percussion• Cartridge and breech

loading• Revolver, semi-

automatic, and automatic handguns

#62. FIREARMS• Long guns – use 2 hands, longer barrel

makes shots more accurate–Rifles: bullets; would will be small and

round– Shotguns• Pellets from a shot: wounds will small, superficial, widespread• Slug: wounds are much larger and deep

• Handguns – fired with one hand– Pistols: 10 or more cartridges in clip/magazine– Revolver: 6 cartridges in a cylinder; first

invented by Samuel Colt

Revolver Semiautomatic Fully Automatic

• Grooves are indentations in the rifle’s barrel.

• The ridges (raised areas) that surround the grooves are called lands.– Leave grooves in BULLET

• produce the twisting that adds accuracy.

• This leaves a pattern on the bullet that matches the barrel pattern to a specific firearm.

Rifling: the arrangement of spiral grooves and lands on the inside of a rifle barrel

Bullets, Cartridges, and Calibers OH MY!

• Cartridge—a case that holds a bullet, primer powder, and gunpowder

• The bullet, usually of metal, is out front with the cartridge, holding the primer and propellant powders, behind.

• Headstamp – tells manufacturer, caliber, sometimes year

headstamp

Caliber• Bullets (and their cartridges) are named by

caliber and length.• Caliber —a measure of the diameter of the

cartridge—by hundredths of an inch. (Europeans use the metric system-9 mm)

• Common calibers include: .22, .25, .357, .38, .44, .45

• A .45 caliber cartridge measures 45/100 of an inch in diameter (almost ½ an inch).

• Caliber also refers to the diameter of the inside of a firearm’s barrel; therefore, the caliber of ammunition should match the firearm that shoots it.

• If a bullet is removed from a wound or crime scene, its caliber can link it to the weapon used to fire it.

• The inner surface of the barrel of a gun leaves its markings on a bullet passing through it.

• These markings are peculiar to each gun. Called striations.

• The gun barrel is produced from a solid bar of steel that has been hollowed out by drilling.

• The microscopic drill marks left on the barrel’s inner surface are randomly irregular and serve to impart a uniqueness to each barrel.

#63. Marks on the Spent Cartridge Casings

• The comparison microscope serves as the single most important tool to a firearms examiner.

• Two bullets can be observed and compared simultaneously within the same field of view.

• Not only must the lands and grooves of the test and evidence bullet have identical widths, but the longitudinal striations on each must coincide.

27

• Firing pin marks – appear on the rim

or center of the spent cartridge

– can be used to match a cartridge to a firearm

• Breechblock marks – produced when the

cartridge casing slams backward and strikes the breechblock

• Extractor & ejector marks– striations

Other marks

29

Gunshot Residues • Gunshot Residues (GSR)– Particles of unburned powder and traces

of smoke – Leave traces on the hand, arm, face, hair,

or clothing of the shooter and/or victim

• Chemical testing can detect residue even if removal is attempted

• Distance from victim to shooter can be determined by examining the residue pattern on the victim

http://hyperphysics.phy-astr.gsu.edu/hbase/traj.html

Voy = sin(angle) X Vo

Vox = cos(angle) X Vo

Vo = original velocity