1st Semester 40 - BIOLOGY JUNCTION

Strawberry DNA

Strawberry DNA Extraction

Adapted from a lab by C. Sheldon

Introduction:

DNA is found in cells from Animals and Plants. DNA is a double stranded macromolecule composed of nucleotide bases pairing Adenine with Thymine and Guanine with Cytosine. DNA can be extracted from cells by a simple technique with household chemicals, enabling students to see strands of DNA with the naked eye.

Purpose:

To extract DNA from the fruit of a strawberry plant

Safety Precautions:

Do not eat or drink in the laboratory.
Wear Apron & Safety Goggles.

Materials / Equipment (per student group):

1. heavy duty zip-lock baggie

2. 1 strawberry (fresh or frozen and thawed)

3. cheesecloth

4. funnel

5. 100 ml beaker

6. test tube

7. wooden coffee stirrer

8. DNA Extraction Buffer (One liter: mix 100 ml of shampoo (without conditioner), 15 g NaCl, 900 ml water OR 50 ml liquid dishwashing detergent, 15 g NaCl and 950 ml water)

9. Ice-cold 95% ethanol or 95% isopropyl alcohol

Procedure:

1. Place one strawberry in a zip lock baggie and carefully press out all of the air and seal the bag.

2. Smash the strawberry with your fist for 2 minutes.

3. Add 10 ml extraction buffer to the bag and carefully press out all of the air and seal the bag.

4. Mush again for one minute.

5. Filter through cheesecloth in a funnel into beaker. Support the test tube in a test tube rack.

6. Discard the extra mashed strawberry.

7. Pour filtrate into test tube so that it is 1/8 full.

8. Slowly pour the ice-cold alcohol into the tube until the tube is half full and forms a layer over the top of the strawberry extract.

9. At the interface, you will see the DNA precipitate out of solution and float to the top. You may spool the DNA on your glass rod or pipette tip.

10. Spool the DNA by dipping a pipette tip or glass rod into the tube right where the extract layer & alcohol are in contact with each other. With your tube at eye level, twirl the rod & watch as DNA strands collect.

Prelab:

Take a look at the sketch of the plant cell below. The chromosomes (which are made of DNA) are in the nucleus. This is the only place where DNA is located.

Now match the procedure with what it is doing to help isolate the DNA from the other materials in the cell.

_____1. Break open the cell	A. Squish the fruit to a slush
_____2. Dissolve cell membranes	B. Filter your extract through cheesecloth
_____3. Precipitate the DNA (clump the DNA together	C. Mix in a detergent solution
_____4. Separate organelles, broken cell wall, and membranes from proteins, carbohydrates, and DNA	D. Layer cold alcohol over the extract

DNA Extraction Table

	AMOUNT ADDED OR OBTAINED	INITIAL COLOR	PURPOSE
BUFFER (soap-salt mixture)
STRAWBERRY
COLD ALCOHOL
DNA

SKETCH OF TEST TUBE WITH CONTENTS

Questions:

1. Where can DNA be found in the cell?

2. Discuss the action of the soap (detergent) on the cell. What is the purpose of the soap in this activity?

3. What was the purpose of the Sodium Chloride? Include a discussion of polarity and charged particles.

4. Why was the cold ethanol added to the soap and salt mixture?

5. Describe the appearance of your final product?

6. Draw a diagram of DNA containing 5 sets of nucleotide bases labeling the hydrogen bonds between the bases.

Properties of Living Things

Properties of Living things

· Early Views of life

o Vitalism:

§ Life was generated by a objects acquisition of “Ethers” which would manifest animate it.

§ Led to idea of spontaneous generation

· Flies came from dead animals

· Mice came from Hay

§ Idea was challenged by scientist Francesco Redi in 1698.

· Designed an experiment where 3 jars contained meat.

o One Jar contained meat and had an open top which would allow the passage of “ethers” and flies. (maggots would appear on the meat)

o The second jar was covered with an airtight lid allowing the passage of neither “ethers” or flies. (no maggots would appear on the meat)

o The third was covered by a screen allowing passage of “ethers”, but not flies. (no maggots would appear on meat)

Setup 1 Setup 2 Setup 3

o Since the third setup would theoretically allow the passage of “ethers”, but no maggots appeared, it was implied that flies were the source of the maggots.

· Led to the theory of Biogenesis

o All life comes from preexisting life

PROPERTIES of LIFE

1. Be made of Cells.

· The Cell is the basic unit of life

· Is self contained and possesses a barrier (membrane) which separates itself from the environment.

· Two types of organisms.

· Unicellular – One celled organism (Uni=1)

· Multicellular – Many cells (Multi=”many”)

2. Living Things must Reproduce.

· Must be able to create more of it’s own kind

· Two types of reproduction:

· Sexual – Two parent organisms combine genetic material to produce the offspring.

· Asexual – When a single organism can divide or “bud” to create it’s offspring without another of it’s species.

3. Living things must Have DNA.

· (Universal Genetic Code?)

4. Living things must Grow & Develop.

· Growth refers to two processes.

· Increase in the number of cells.

· Increase in the size of cells.

· Development refers to changes in the organism which occur through it’s life-span.

· Includes cell differentiation.

· Includes organ development

· Includes aging & death.

5. Living things obtain & use energy.

· Energy is used by all living things for growth, development & reproduction.

· Life processes which result in “building” the organism ia known as Anabolism.

· Life process where energy is extracted by “breaking-down” substances is called Catabolism.

6. Living things must Respond (or react) to their environment in some way.

· Something which causes an organism to react is known as a Stimulus (stimuli).

· The ability of an organism to react is called Irritability.

· Most responses are geared for maintaining Homeostasis.

· Homeostasis is a process where an organism maintains a stable internal environment so life can continue.

· Some examples include temperature, pH, and water content of the cell.

7. Must Maintain homeostasis.

· Internal stable set of internal conditions allowing the chemical reactions of life to occur.

Scientific Laws

Scientific Laws, Hypotheses, and Theories

Scientific Theory versus “Just a theory” Layman’s term:

In layman’s terms, if something is said to be “just a theory,” it usually means that it is a mere guess, or is unproved. It might even lack credibility. But in scientific terms, a theory implies that something has been proven and is generally accepted as being true.

Scientific Meanings:

SCIENTIFIC LAW: This is a statement of fact meant to describe, in concise terms, an action or set of actions. It is generally accepted to be true and universal, and can sometimes be expressed in terms of a single mathematical equation. Scientific laws are similar to mathematical postulates. They don’t really need any complex external proofs; they are accepted at face value based upon the fact that they have always been observed to be true. Specifically, scientific laws must be simple, true, universal, and absolute. They represent the cornerstone of scientific discovery, because if a law ever did not apply, then all science based upon that law would collapse. Some scientific laws, or laws of nature, include the law of gravity, Newton’s laws of motion, the laws of thermodynamics, Boyle’s law of gases, the law of conservation of mass and energy, and Hook’s law of elasticity.

HYPOTHESIS: This is an educated guess based upon observation. It is a rational explanation of a single event or phenomenon based upon what is observed, but which has not been proved. Most hypotheses can be supported or refuted by experimentation.

THEORY: A theory is more like a scientific law than a hypothesis. A theory is an explanation of a set of related observations or events based upon proven hypotheses and verified multiple times by detached groups of researchers. One scientist cannot create a theory; he can only create a hypothesis. Theories may be expanded or modified with further scientific evidence.

Development of a Simple Theory by the Scientific Method:

Start with an observation that evokes a question: Broth spoils when I leave it out for a couple of days. Why?
Using logic and previous knowledge, state a possible answer, called a Hypothesis: Tiny organisms floating in the air must fall into the broth and start reproducing.
Perform an experiment or Test: After boiling some broth, I divide it into two containers, one covered and one not covered. I place them on the table for two days and see if one spoils. Only the uncovered broth spoiled.
Then publish your findings in a peer-reviewed journal. Publication: “Only broth that is exposed to the air after two days tended to spoil. The covered specimen did not.”
Other scientists read about your experiment and try to duplicate it. Verification: Every scientist who tries your experiment comes up with the same results. So they try other methods to make sure your experiment was measuring what it was supposed to. Again, they get the same results every time.
In time, and if experiments continue to support your hypothesis, it becomes a Theory: Microorganisms from the air cause broth to spoil.

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Safety Guidelines

Safety goggles/glasses & aprons must be worn at all times in the laboratory.
Tie back long hair & secure lose clothing.
No horseplay is allowed in the lab.
No food or drink is allowed in the laboratory.
Practice good “housekeeping” techniques. Return items to proper places in good condition. Avoid cluttering your work area.
Never use chemicals from unlabeled containers. Check each label before dispensing a chemical, & do not return a chemical to a bottle without the teacher’s permission.
Unless told otherwise, treat all chemicals as poisonous or corrosive. Wash hands immediately with plenty of water if chemical gets on them and always wash your hands before leaving lab.
No unauthorized lab work may be done, & a teacher must be present to do lab work.
Read & study each lab assignment before coming to lab. Pay attention to safety notes in the lab manual and from the instructor. Some common lab concerns:
* Never pipette by mouth
* Never use chipped or cracked glassware
* Do not heat a closed system
* Do not point heated containers at yourself or another person
* Use a fume hood for noxious fumes
* Place heated glass on wire gauze until cool
* Do not use flammable material near open flame
* Wear gloves when dispensing irritating chemicals
* Dilute concentrated acids by adding acid to water
* Turn off burners and water faucets when not in use & before leaving lab
* Only heat glassware marked Kimex or Pyrex
* Use glycerin and a twisting motion to insert glass tubing into stoppers
* Use tongs, test tube holders, or heat-resistant gloves to handle hot glassware
* Use pins to secure dissecting organisms to the dissecting tray before cutting with a scalpel
* Wash hands before and after dissecting and keep hands away from your face
Report all accidents immediately to the teacher.
Know the location and proper use of all safety equipment in the lab.
Know where all exits are from the lab.

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Scientific Equipment

Scientific Equipment All Materials © Cmassengale
Click HERE for Notebook Copy
	Compound Light Microscope (LM)-used to enlarge an image		Graduated Cylinder – used to measure the volume of liquids
	Microscope Slide – supports an item being examined under the microscope		Cover slip – covers specimen on a slide
	Beaker – holds liquids while they are being stirred or heated		Test Tube Brush – used to clean test tubes
	Evaporating Dish – used for heating solids		Pinch Clamps – used to control the flow of liquids through tubing
	Funnel – assists in transferring liquids to containers with smaller openings		Striker – used to ignite a burner
	Test Tubes – holds liquids for observation or testing		Safety goggles – protects the eyes from damaging substances
	Pipet pump – dispenses known volumes of liquids		Eyedropper – used to transfer small amounts of liquids
	Forceps – used to hold or lift specimens		Magnifying glass – enlarges the image of an object
	Crucible – containers used for “strong” heating		Test Tube Rack – holds test tubes during observation or testing
	Wash Bottle – used for rinsing solids out of a container		Pipet – used for exact measurements of liquids
	Spatula – chemical spoons used to transfer solids from their original container to a scale for weighing		Wire Gauze – adds additional support for containers held on tripods or O-rings
	Crucible Tongs – used for picking up crucibles & crucible covers only		Mortar & Pestle – used to grind solids into powders
	Florence Flask – used to store liquids		Erlenmeyer Flask -used to store solutions
	Dissecting Pan – holds specimen being dissected		Test Tube Holder – holds test tubes while heating
	Electronic Balance – used for weighing substances		Bunsen Burner – heat source
	Thermometer – used to measure temperature	Stopper – used to cap flasks containing liquids
	Scalpel – used for cutting specimens being dissected		Tubing – hose used for connecting glassware
	Petri Dish – plate used to culture microorganisms		Triple Beam Balance – used for weighing substances
	O-Ring – used with ring stands to support heated vessels		Volumetric Flask – used to mix precise volumes of liquids
	Watch Glass – used on top of beakers when heating	Desiccators – used to remove moisture from substances
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