qwerty

DNA module- DAY I: Hair analysis and DNA extraction
Forensic science
The story:-127009969500 This weekend, biology teacher Prof. Morra was found dead in his apartment. His body was found around 9.00 am by his girlfriend, who immediately phoned the police. The police found Prof. Morra lying beside his bed, a noose around his neck. At that point it was not clear whether he had been murdered or had tried to commit suicide. There was blood around his face and neck. His hands were covered in blood and hair.
A few days later police reported that they had found a sample of blood at the crime scene that was not the victim’s, and which could be key in leading them to the perpetrator. The hair found on the victim’s hands had been analyzed, and found to belong to the same person as the blood.
The police were in the process of interviewing a list of people:
Maria Morris: the girlfriend. She was also a biology teacher, but at another college. They had been dating about a year; she had a key to his apartment. She told police that she had returned late from a conference the night before, and had tried phoning Prof. Morra from the airport around midnight. He did not pick up, she figured he had fallen asleep, and she would find him in the morning. That morning, she had tried calling him again at home, on his cell and at his office. Therefore, decided to drop in.
She informed the police that Prof. Morra had been previously married and was going through a messy divorce. His wife lived a few miles away.

Samuel Massey: a student. Police interviewed faculty and the chair of Prof. Morra’s department. Prof. Morra appeared to be well liked by his colleagues. He had a good reputation as a teacher, but demanded a large amount of work from his students. The chair informed the police, that a few days ago, an extremely angry student, Samuel Massey, had had an encounter with Prof. Morra. The student had failed his class, and therefore had not been accepted into nursing school. Police visited Samuel’s home, but did not find him. His mother told them that he had gone fishing the week of the murder; she said that her son would never murder anyone. She told police that Samuel had been upset that he did not get into nursing school, and since had been spending much time with his friends; some nights he did not come home. Days later, police found Samuel. He denied committing the murder. A friend of his, whom the police questioned, said that they had been fishing that week.
Vilma Morra: the ex-wife. She had custody of their only daughter. She told police that her husband had been a month late on his monthly payments to support their daughter. She said that she had been in his apartment on Friday night demanding money. She claimed that even though she hated her husband, she had not killed him.
-2838456858000Elaine Cook: the neighbor. She lived in the apartment below Prof. Morra. She said she occasionally talked with Prof. Morra. He mostly kept to himself. The night before his body was found, she had heard major arguments and shouting from his apartment. She heard several people go in and out of his apartment. She remembered that a few months ago, she had talked to Prof. Morra; he had been very upset. He told her that all faculty in the University System of Georgia had to take a 50% salary cut, due to the recession.
James Taylor: the apartment manager. He told police that Prof. Morra had been 2 months late on his rent payments. He told police that he had visited Prof. Morra the night before the murder with an eviction notice. He and the Prof. had got into an argument, but he claimed he did not commit the murder.
DNA evidence
-571502794000Deoxyribonucleic acid (DNA) can be considered the hereditary “code of life” because it possesses the information that determines an organism’s traits and is transmitted from one generation to the next. DNA can be compared to a recipe or a list of instructions about how to create and maintain a specific living thing. The DNA in an individual’s cells contains unique genetic instructions about how to make and operate that individual.
All living things are dependent on DNA, and the structure of DNA is consistent among all species. However, the particular sequence of nitrogenous bases within DNA molecules differs between organisms to create explicit “blueprints” that specify individual living things. This sequence of base pairs is what makes an organism an oak tree instead of a blue jay, a male instead of a female, and so forth.
Plants, animals, protists, and fungi are all made up of eukaryotic cells that have a nucleus encased by a nuclear membrane. In these cells, DNA is packaged within the nucleus. Bacteria and cyanobacteria are made up of prokaryotic cells. These types of cells do not have a nucleus. Instead, the DNA in prokaryotic cells is found in a long loop coiled loosely throughout the cell’s cytoplasm.
Two tissue samples were found at the scene. One belongs to the victim, Dr. Morra. The other belongs to someone else who was at the scene at the time of the murder. We will compare the DNA from these samples to the suspects to determine if one of them was at the scene and somehow left his or her blood behind. Since we are only interested in the DNA from the sample, we must first extract that DNA (i.e., separate it from the rest of the tissue sample). Today, you will practice DNA extraction using strawberries. We will use the DNA from the scene later this semester.
Strawberry DNA extraction
4838700171767500All cells of all organisms have DNA (at least at first). In order to study an organism’s DNA, we must first get it out of the cell. DNA extraction is a fundamental procedure in scientific laboratories around the world. By extracting DNA, scientists can learn how DNA encodes the instructions for all life processes. DNA extraction is important to the study of heredity and to the treatment of many diseases through the creation of gene therapy DNA molecules. Extracted DNA can also be used to create DNA fingerprints to help diagnose genetic diseases, solve criminal cases, identify victims of disaster and war, and establish paternity or maternity. Scientists can genetically engineer changes in DNA to create robust, disease-resistant genetically modified plants and animals. DNA extraction is also necessary in order to sequence the DNA code (order of base pairs) of different organisms (as in the Human Genome Project) and compare different species.
Procedure
Obtain one fresh or one frozen and thawed strawberry. If you are using a fresh strawberry, remove the green sepals (tops) from the berry.
Place the strawberry in a re-sealable plastic bag.
Close the bag slowly, pushing all of the air out of the bag as you seal it.
Being careful not to break the bag, thoroughly mash the strawberry with your hands for two minutes. This begins the process of lysing (or breaking open) the cell membranes of the strawberry’s cells and nuclei exposing the DNA.
Pour the 10-mL aliquot (i.e, a sample or a portion of the total amount of a solution) of extraction buffer into the bag with the mashed strawberry. Reseal the bag.
Mash the strawberry for one additional minute. The buffer (in this case a type of detergent) and more mashing further break apart the membranes of the strawberry cells and nuclei by dissolving the phospholipids that make up the membrane. Salt in the buffer causes the broken up parts of the cell to separate from the DNA.

5123180444500Place a funnel into a 50-mL centrifuge tube. Fold a piece of cheesecloth in half along the longer side and place it in the funnel to create a filter. The cheesecloth will overlap the edge of the funnel.
Pour the strawberry mixture into the funnel, filtering the contents through the cheesecloth and into the 50-mL centrifuge tube. The cheesecloth filters the unwanted cell fragments, which can be seen and are stuck in the cheesecloth, from the DNA, which passes right through.
-31115037465000Carefully pour 2 mL of the filtered contents from the 50-mL tube into a clean 15-mL tube. Use the lines on the side of the 15-mL tube to help measure the amount added.
533527073850500Hold the 15-mL tube at an angle. Using a transfer pipet, carefully add 5 mL of cold 95% ethanol by running it down the inside of the tube. Add the 95% ethanol (EtOH) until the total volume is 7 mL (use the lines on the side of the tube to help you measure). Alcohol separates the DNA from the rest of the cell extract that made it through the cheesecloth. You should have two distinct layers. Caution: Do not mix the strawberry extract and the ethanol!
Watch closely as translucent strands of DNA begin to clump together where the ethanol layer meets the strawberry extract layer. Tiny bubbles in the ethanol layer will appear where the DNA precipitates.
Slowly and carefully rotate the wooden stick in the ethanol directly above the extract layer to wind (or “spool”) the DNA. Remove the wooden stick from the tube and observe the DNA. You can set the DNA on a paper towel.
This DNA comes from multiple strawberry cells. Strawberry cells are excellent sources of DNA for extraction. They are multicellular and octoploid. This means they have eight copies of their seven chromosomes in each of their many cells. Therefore, just one berry will yield enough DNA to be easily seen and spooled.

4717415-17780000Physical evidence:
Before there was complex DNA analysis, forensic scientists used physical evidence collected at the scene to determine if the victim came into contact with any specific suspect. Forensic scientists amassed amazing skills that allow them to read the history of tire tracks, blood splatter, ricocheted bullets, torn fabric, and even hair. Today, you will be using your microscope skills to analyze hair from an unknown person that was collected at the crime scene.
Here’s what we can tell from hair samples:
Hair scale shape coronal (crown-like) imbricate (flattened) imbricate centercenter00 centercenter00
Many animals Many animals and humans Human hair
Medulla- central core of cells
Various types Human hairs In animals, it is usually regular, well-defined In humans, it may not be present, but when it is, it is often amorphous
Color
2768609017000Animal Natural human hair Dyed human hair Multi-colored along length.
Densest at medulla. Uniform color along length, but not in the cuticle. Densest at base. Uniformly colored, including the cuticle
Edge
Scissor cut Razor cut Broken Burned Point of origin
Head Pubic Limb Beard Race
African Asian Caucasian Hair Analysis
Each group is assigned a suspect. Your task will be to make a series of observations to determine whether the hair found at the scene matches your suspect. You will be comparing this hair to Prof. Morra, since it is his apartment, we expect to find a lot of his hair.
Procedure
Analyze the hair sample from the suspect(s) and compare it to the one found at the crime scene and to hair from Prof. Morra. Use your compound microscope to visualize the hair samples. Use the 4X, 10X and 40X objectives. Take good notes about the structures of each sample.

DNA Day I Questions Name ______________________________
Since you’ve extracted DNA from a cell, in your opinion how tough is DNA compared to other components of the cell?
Describe the color, texture, thickness and other features of the unknown hair and the hairs from the known individuals, your suspect, and Professor Morra.
Is your suspect a match for the unknown hair? What does this mean?