DNA Extraction

DNA Extraction:

Scientists isolate DNA for:

1. Genetic testing

2. Body identification

3. Analysis of forensic evidence

DNA extraction is important because the DNA first needs to be purified away from proteins and other contaminants.

Steps:

1. Collect cells from test subject

2. Burst cells open to release DNA

3. Separate DNA from proteins and debris

4. Isolate concentrated DNA

2. Burst cells open to release DNA

Lysis solution:

Contains -

Detergent

The detergent disrupts the cell membrane and nuclear envelope, causing the cells to burst open and release their DNA.

Enzyme called proteinase K

The DNA is still wrapped very tightly around proteins called histones, and the proteinase K cuts apart the histones to free the DNA.

3. Separate DNA from proteins and debris

Salt solution:

Salt causes proteins and cellular debris to clump together.

Centrifuge:

- When placing the tube containing the DNA into the centrifuge, a tube containing water is placed opposite the tube in order to ‘balance’ it.

- Inside the centrifuge, the tubes are spun around at high speed, which causes the heavy clumps of protein and debris to sink to the bottom, while the strands of DNA remain distributed throughout the liquid. The DNA can then be separated from the proteins and debris.

4. Isolate concentrated DNA

Isopropyl alcohol/ethanol:

DNA is not soluble in isopropyl alcohol and so it comes out of the solution. When put into the centrifuge again, the DNA settles at the bottom of the tube instead.

Notes taken from http://learn.genetics.utah.edu/content/labs/extraction/ when completing the DNA Extraction Virtual Lab Activity :)

Basics of DNA, Genes, Chromosomes, Heredity and Traits

DNA:

Instructions providing all the information necessary for a living organism to grow and function reside in the nucleus of every cell. The instructions come in a form called DNA. DNA encodes a detailed set of plans, like a blueprint, for building different parts of the cell.

The DNA molecule comes in the form of a “double helix”, built with the four-letter DNA alphabet: A, C, T, and G. A always pairs with T, and C always pairs with G.

G = Guanine

A = Adenine

T = Thymine

C = Cytosine

The DNA strand is made of letter, which form words, which then form sentences. These “sentences” are called genes.

Genes:

Genes are made of DNA. One strand of our DNA contains many genes. Genes are the directions for building all the proteins that make our bodies function. All these genes are needed to give instructions for how to make and operate all parts of our bodies. Proteins enable a cell to perform specific functions, such as working with other groups of cells to make hearing possible.

Chromosomes:

Each cell in our body contains a lot of DNA, thus chromosomes are used to compact DNA so that it can fit into a cell.

Packaging of DNA into a chromosome:

1. Double helix of DNA

2. DNA is wrapped around proteins

3. Proteins are packed tightly together until they form a chromosome

Heredity:

The passing of traits from parents to child is the basis of heredity.

How do we get traits from our parents?

Humans have two complete sets of 23 chromosomes (2 x 23 = 46 total)

Each child receives half of its chromosomes from the mother and half from the father.

When parents conceive a child, they each contribute one complete set to the child. This one set can contain chromosomes from both of the parent’s two sets.

Since the parents contribute chromosomes randomly to each new child, every child inherits a unique set of chromosomes and thus has a unique combination of traits.

Traits:

A trait is a notable feature or quality in a person. Each of us has a different combination of traits that makes us unique.

Physical trait:

Characteristics of one’s physical makeup e.g. eye colour, hair colour, height etc.

Behavioural traits:

Characteristics of the way one acts e.g. sheepdog’s herding instinct, a retriever’s desire to fetch etc.

Predisposition to a medical condition:

An increased risk of getting a certain type of disease is also a type of trait that can be passed from parent to child. E.g. sickle cell anemia, cystic fibrosis, heart disease, cancer, certain mental illnesses etc.

Genes encode the instructions that define our traits. The environment we live in also helps to define our traits. For example, while a person’s genes may specify a certain hair colour, exposure to chemicals or sunlight can change that colour.

Set of genetic information for each form - Allele

E.g. Straight thumb allele - “H” (dominant)

Hitchhiker’s thumb allele - “h” (recessive)

Each of us has two alleles for the thumb extension trait. We all have one of 3 possible combinations:

H + H = H

h + h = h

H + h = H --> The dominant gene will be exhibited as the trait

Two of the same allele for a trait - homozygous

Two different alleles for a trait - heterozygous

How are traits inherited?

Mother and father each have two alleles for the thumb extension trait. When they have a child, they pass one of their alleles to their child. The child’s trait is determined by the alleles he/she receives from his/her parents. Each child from these parents can receive a different combination of alleles.

Are all traits inherited this simply?

No. The thumb-extension trait is a well-defined physical trait, however most traits are more complex and thus cannot be tracked through generations this easily.

Alleles can work together to produce incomplete dominance e.g. crossing a red carnation and a white carnation can produce a pink one.

Single-gene traits:

Traits influenced by just one gene. They are rare.

Complex traits:

Traits shaped by more than one gene, sometimes many.

Notes taken from http://learn.genetics.utah.edu/content/begin/tour/ while completing the tour :

Blood Splatter Experiments

Experiment 1:

Experiment 2:

Look out for pictures of the experimental setup and the blood splatters, as well as part 2 soon! :)

Blood Splatter

These were discussed and generated by my partner, Cheryl and I so we both have similar answers:

Blood splatter 1: The shape of the blood splatter is one large drop of blood with small drops surrounding it. This

is probably created by drops of blood dropping onto a same spot. This means that the surrounding drops of blood are the result of blood dropping onto other drops of blood already on the surface and thus the impact resulting in small drops of blood being scattered around.

Blood splatter 2: This blood splatter consists of 2 main areas which contain larger amounts of blood and small droplets of blood surrounding them. As the drops of blood are not complete, they look like they may have been smudged, such as by another object coming into contact with the splatter. May have been created through a gunshot?

Blood splatter 3: The shape of the blood splatter is long and slants slightly upwards from left to right, and is more narrow on the left side than the right side. This means that the direction of the blood was north east. This splatter is most likely created by blood being flung off a swinging item that was bloody.

Blood splatter 4: The blood splatter covers a large area and consists of many smaller oval shaped splatters which have drops of blood dripping downwards. The splatter looks like it was created intentionally due to the relatively regular pattern of the blood splatter. It could have been created using a product such as red paint.

Blood Splatter Pattern from a Laboratory Experiment:

What is the shape of the blood splatters?

Circles and ovals, of varying lengths and widths.

Describe any other characteristics of the splatter.

- Jagged edges

- 2 distinct areas(inner and outer) the inner portion being a darker colour than the outer portion

- blood dropped vertically creates a blood splatter in the shape of a circle while blood dropped an an angle creates one that is in the shape of an oval, with increase in angle causing increase in the length and decrease in diameter of the blood splatter.

What are the factors that affect the shape of the blood splatter? Name as many as possible.

- angle at which the blood drop reaches the place of contact

- the distance blood is dropped at from the point of contact

- the surface of point of contact

- amount of blood that is dropped

- force used to create blood splatter(high impact/low impact)

- viscosity of blood used

Generate some hypotheses from the blood splatter patterns observed above.

1) The greater the height from which the blood is dropped, the larger the size of the blood splatter

2) The greater the angle of the plane used, the greater the length of the blood drop and the smaller the width of the blood drop

3) When a droplet of blood strikes a horizontal surface at 90 degrees it produces a circular stain. While droplets of blood that strike the surface at an angle produce a oval shaped stain

2. If dropped from the same height from the plane, the length of the blood drops will increase and the width of the blood drops will decrease as the angle of the plane on which the blood is dropped increases.

Chromatography

Below is the table of results for my pair's (Cheryl and I) chromatography:

Trace Elements - Flame Test!

OBSERVATIONS

Below are my group's observations of the colours of the flame when different elements were used:

Barium - Yellow

Calcium - Red-Orange

Copper - Green

Lead - White-Pink

Potassium - Pinkish-Orange

Sodium - Orange-Yellow

And here are the answers provided by Ms Tan as to what the colours should be:

Barium - Pale/Yellow-Green

Calcium - Orange-Red

Copper - Blue-Green

Lead - White/Blue

Potassium - Lilac to Red

Sodium - Intense Yellow

Magnesium - Bright White

Possible reasons for the differences could be due to:

- The contamination of the bunsen burner, where other elements could have dropped into the bunsen burner, causing the flame colour to change

- My group's perception of the colour of the flame could have been different

QUESTIONS and ANSWERS

1. How and what is it (flame test) used for in "crime scene investigations/forensic science"?

They are used to identify different elements found in a sample collected at a crime scene. Since the sizes of the possible jumps in energy terms vary from one metal ion to another when heated, different ions will have a different pattern of spectral lines, and so different flame colours. These different flame colours are used to identify elements. The flame colours of the elements in the sample collected at the crime scene can then be compared to the known colours of different elements, thus identifying the elements found in the sample and narrowing the search for the culprit.

2. If there are more than one trace metal present, is the flame test still a suitable technique to identify the trace metals?

No. There would be a mix of colours, making it difficult to identify the different elements. We would be unable to tell if the colour was produced as a combination of colours produced by different elements (e.g. Sodium that is yellow combined with Lead that can be white or blue may produce a green flame)

3. Is a flame test sufficient to identify the trace metal(s) present?

Although it may help to narrow down the spectrum of elements involved, it is not sufficient to identify the trace metals present solely based on a flame test. This is because some elements produce highly similar colours and others do not change the colour of the flame. Furthermore, the colour of the flame produced by the trace element is subject to our perception, making it very relative and not completely accurate.

4. What is a "Mass Spectrometer"?

The mass spectrometer is an instrument which can measure the masses and relative concentrations of atoms and molecules. It makes use of the basic magnetic force on a moving charged particle.

In order to measure the characteristics of individual molecules, a mass spectrometer converts them to ions so that they can be moved about and manipulated by external electric and magnetic fields. The three essential functions of a mass spectrometer, and the associated components, are:

1. A small sample is ionized, usually to cations by loss of an electron. The Ion Source
2. The ions are sorted and separated according to their mass and charge. The Mass Analyzer
3. The separated ions are then measured, and the results displayed on a chart. The Detector

This website is very useful for understanding the basic principle behind the mass spectrometer as well as how it works: http://www.chemguide.co.uk/analysis/masspec/howitworks.html

Fingerprinting

Answers to questions:

Ridges and Pores Activity:

Q. Where are the pores found? Are they regularly spaced?

A. They are found on the ridges of our fingers. Yes, they are, but may sometimes be erratically or randomly positioned.

Q. Are the lines of your print equally spaced throughout?

A. Mostly, but there are places where the lines merge, changing the distance between the lines. At other places the lines may not be curved in the same way as the rest, bending a different direction and thus causing the distance between the lines to change.

Cyanocrylate (Superglue) Fuming Method:

Q. If the contrast of the white print against the background is still too faint for a good photograph to be captured, what could be done to enhance the fingerprint?

A.

1. A greater amount or greater concentration of superglue could be used

2. The finger used to create the print could be made more oily first to enable a more distinct and clear print to be made

Iodine Fuming Method:

Q. What are the possible substances that may be used to render the prints more permanent?

A. The material used for printing the fingerprint on probably affects the time the print stays on it. To make the prints more permanent, they can be treated with a starch solution. Iodine and starch combine to form a deep blue-black complex, which persists for weeks to months, depending on storage conditions. Benzoflavone can also be used to treat prints to render them permanent.

Q. Why does the print disappear?

A. The natural body fats and oils in the latent print only temporarily absorb the iodine vapours when placed in the environmet containing the vapours (i.e. the gas jar), once removed from that particular environment, the vapours eventually dissipate back into the atmosphere and thus fade.

Powder Dusting Method:

Q. What is magnetic powder dusting and how does it work?

A. A magnetic applicator is used to attract magnetic powder, which is then lightly dusted over the fingerprint. It is usually used on non-magnetic, shiny surfaces such as plastic containers.

My own Fingerprint Database: Observations

1. Compare the fingerprint patterns on your right and left hand. Are they mirror images of each other?

My right and left thumbs can be considered mirror images of each other. However, the other fingers are definitely not mirror images of each other.

2. What kind of patterns do you see?

There are loops and whorls, but no arches.

3. Do the loops curve in the same or different directions in different fingers?

They are different for different fingers because no two prints are the same. One interesting thing observed is that most prints made by the left hand curve to the left and those on the right curve to the right.

4. Compare the size of the patterns e.g. How many ridges make up a loop?

Some fingers have more ridges making up the loop while others have fewer and thus smaller loops. They are not the same.

Interactive Investigator

Physical Evidence:

Hair

Fibre

Footprints

Scratch mark

Letter

Fingerprint

Blood stain

Wound

Paint chips

Fields:

Pathology

Forensic Sciences

Coroner

Ballistic

Uses of evidence:

Footwear impressions allow you to match the impression with actual footwear owned by suspect.

Toolmark impressions allow you to match the impression with actual tools owned by suspect.

Paint examination allows you to match a tool to the crime scene, when the tool is found.

Computer composites can help with suspect identification.

Hair analysis enables comparisons with the suspect's hair or with hair found on the suspect's clothing

Document analysis can verify the authenticity of a document and who the author is.

Fingerprint analysis is still the predominant means of establishing positive identification.

Fiber analysis rests on the principle that whenever two individuals are in contact, materials (dust, paint, cloth...) are exchanged at a microscopic level.

Blood stain pattern analysis tells you how a crime was committed.

Blood analysis lets you identify a victim or a suspect, because DNA is unique to each individual.

Wound analysis can help with identifying the murder weapon.

Pathology allows you to establish time of death and compare with suspect's schedule.

__________________________________________________________________

Evidence found

Place of entry:

Footwear impression:

- photographed with and without a ruler, taken from all sides

- castings made

- footwear acquires individuality as it is worn down --> defects such as cuts and abrasions occur

- footprint left behind was worn at the heel --> suggesting that the suspect drags his feet

What to do with information:

When a suspect is found, his/her home and/or place of employment should be searched in order to find boots that match the impression at the lab.

Lock on back door was forced open by a tool:

- someone was determined to get inside

Since entire door cannot be removed,

- photographs taken

- silicone impressions of the grooves left by the tool used are made

- identify tool by comparing tools and other marked objects

3 types of tool mark impressions:

Compression: tool surface presses into a softer material

Sliding: tool scrapes across a surface causing parallel striations

Cutting: combination of compressing and sliding

Mark impressions left by tool used by suspect:

Compression: tool made slight indentation in wood

Sliding: in the metal surrounding impression

Tool used --> crowbar

What to do with information:

Search all suspects' homes in order to find a match for the tool.

Paint chips:

- Often found when a tool is used on a painted surface

- Minute traces of the paint, when the tool is found, can be matched to the crime scene.

- Minute traces may also be found on a suspect's clothes or person.

- Matching is done using the concepts of class and individual characteristics. This methodology also applies with incidents involving motor vehicles.

How to collect evidence: holding a paper bindle open and scraping chips into it with a clean knife type blade

What to do with information:

Look for minute traces of this same paint on the tool used to break into the house (if it is found) or on the suspect's clothes.

Imagery and Computer Composite:

If there is a witness to the suspect, the witness will be asked to describe as much as possible about the suspect. A forensic artist will then do a composite drawing of the suspect either

- manually

- using a computer imagery

- both

Computer imagery:

- Database of many styles of facial features available

- Showing them to a witness enables the witness to come up with a clear image.

- The artist also notes height, weight, hair colour, eye colour, gender, race, and age of the suspect.

- The artist's success comes from listening very carefully to the witness.

- With a composite drawing, the Police have a much better chance of finding a suspect.

What to do with information:

Use these sketches to see if anyone recognizes who these women are and thus give them an identity.

Place of struggle:

Living room: Struggle between suspect and victim

Hair:

Can tell:

- race

- if the person has any drugs, poisons, or diseases in their system

- can ultimately be matched to a suspect

Why can these factors be revealed?

Hair contains DNA, and DNA encodes information that determines a person's genetic makeup. The reason hair can tell the forensic specialist what race a person belongs to, for example, is because all people within a particular race have a similar DNA code sequence, as everyone who has brown hair has a similar code sequence for brown hair. The coding sequences, however, are separated by 'junk' DNA. This 'junk' DNA is non-coding and separates coding sequences. The 'junk' DNA sequences are random and unique to each person. This is why hair can identify its owner.

What to do with this information:

If the woman with the red hair is found, and becomes a suspect for the murder, the investigators should get a warrant allowing them to obtain a DNA sample from her. The sample will then be compared to those found at the crime scene.

Document Analysis:

How documents at a crime scene are collected:

They are placed in cellophane or plastic envelopes, and are never marked, defaced, altered, or folded. At the lab, they analyze the paper, ink, and handwriting.

Questioned documents:

Forensic Science disciplines:

- paper and inks

- handwriting analysis

- writing instruments

- typewriting

- photocopying

- computer printers

- computer disks

- forgery

- gambling machinery

- rubber stamps

- dating of documents

Handwriting analysis:

Examines -

- design

- shape

- structure

to determine authorship

Graphology - not a forensic science but a study of a person's handwriting to determine their personality traits

What to do with this information:

Go to the shop (that the paper was sold at) and ask if any of the sales clerks recognize the sketches of the two women who were seen at the victim's house on the day of the murder.

Fiber Analyis:

"Locard's Exchange Principle": when someone comes in contact with another person or place, something of that person is left behind, and something is taken away.

It utilizes the concepts of class and individual characteristics, thereby determining the type and colour of the fibre.

What to do with this information:

When a suspect is arrested, their home should be searched to find a garment with fibers that match the fiber in the police's possession.

Place of murder:

Bloodstain Pattern Analysis:

Blood reacts, as all liquids do, in a predictable, consistent, reproducible manner. The types of reactions are called 'standards'. These standards can tell the expert how a crime was committed by the stain the blood leaves.

Different splatters occur, for example, when blood falls from different heights.

When there is a blunt force trauma, and blood splatters, the stains left are called 'cast off stains'. Cast off stains reveal:

- direction and number of blows

- size of the object used

- orientation of the person

- if they are right or left handed

Body of victim:

2 puncture wounds:

- Neck

- Heart

--> shows that attacker is experienced and has been in many fights to be able to know where to stab

Splatters on wall:

Suspect stabbed victim in the neck --> hit carotid artery --> blood comes out in spurts --> great loss of blood occurs within only a few seconds if it is a major artery --> victim lost consciousness quickly --> could not defend himself against second attack when suspect aimed for the heart --> victim fell where he stood --> died almost instantly

Direction: lunged forward at victim using a downward motion --> attacker must be at least as tall as victim

Bloodstains:

Neck - accounted for most of the large bloodstain that seeped under the body

Heart - murder weapon nowhere to be found --> suspect pulled knife out from the victim's heart --> heart bled a little --> would have almost no blood if the knife was left in --> because knife would have acted as a plug

What to do with this information:

When a suspect is arrested, they should take into consideration that he or she has to be at least 5'9" tall and with either a criminal record or a self-defence background (such as Martial Arts or military training).

Wound Analysis:

2 puncture wounds made with a switchblade (small pocket-knife)

Nature of wounds indicate that the blade was:

- narrow

- approx. 4 inches in length

- good quality,

blade did not break when victim was stabbed

---> not easy to stab someone in the heart --> must get past thoracic cage which is designed to protect vital organs --> blade went all the way through + tip did not even break --> good quality switch blade

What to do with this information:

When a suspect is found, his/her home and/or place of employment should be searched to find the same type of weapon.

Blood Analysis:

Blood found at a crime scene can tell through chemical analysis if the personhas any drugs or poisons in his or her system. Through DNA analysis a person's genetic make up may be identified. A very important use of DNA typing is the identification of perpetrators of a crime by comparison of biological samples of suspects against biological specimens that the perpetrator of a crime has directly left at the crime scene (e.g. semen, saliva, skin, or blood). The reason blood can tell the forensic specialist what race a person belongs to, for example, is because all people within a particular race have a similar DNA code sequence, as everyone who has brown hair has a similar code sequence for brown hair. The coding sequences, however, are separated by 'junk' DNA. This 'junk' DNA is non-coding and separates coding sequences. The 'junk' DNA sequences are random and unique to each person. This is why blood samples can identify or eliminate a suspect.

What to do with this information: When a suspect is arrested, a blood test may be performed in order to find a DNA match between the suspect's blood and the blood found at the crime scene.

Time of Death:

Tells us what time victim died

Factors considered:

1. Livor mortis (can also show if the body was moved)

Setting of blood in the dependant regions of the body following death

e.g. blood has accumulated in the back of the body

shows that:

- after vicim died, he was lying on his back for several hours

- was not moved after he was killed

2. Rigor mortis

Chemical reaction that causes rigidity in the muscle groups following death.

After half an hour

Muscles go stiff, but then they go limp again

Only after about 12 hours

Body becomes very stiff

3. Algor mortis

Cooling of the body

What to do with this information: Ask the different suspects where they were at the time of the murder, and if anyone can confirm their alibi.

Case of the trash tosser + Awareness Test

Trash found:

Empty glass bottles

Fish bone

Banana peel

Gravy/ Vomit?

Slylock found bones in the trash.

The bull is an herbivore and only eats plants.

The racoon is an omnivore and eats both plants and animals.

Racoon is the trash tosser.

Awareness test:

I did not see the moonwalking bear the first time round because I was completely focused on the passes that the team in white was making and did not want to get distracted by looking at the surroundings. Also, since the bear was black, it was rather hard to spot and went unnoticed because I was only looking at the people in white. Lastly, since the instructions were to count the number of passes that the white team was making, I did not expect a moonwalking bear to appear. I must learn to pay attention to the surroundings while focusing on the task at hand.