BIO150-3 / Report Lab 2: Microscopy and Cell Structure

Lab 2: Microscopy and Cell Structure

 Aim:To observe some different cell types and the organelles they contain. To see firsthand the major differences between plant and animal cells which I will learn about in the BIO 100 lecture course next week. 

Purpose:To become familiar with the use of both compound and dissecting microscopes and to use them to observe cells and biological matter at both the microscopic and macroscopic level. All organisms consist of one or more cells and specific stains an be used to highlight some of the organelles and structures they contain. 

Materials: 

Plant cell materials (onion/potato/weeds from teacher’s garden)

Animal cell materials (cured fish eggs)

Plastic micro-centrifuge tube in which has water fleas in.

Stains (solutions of Iodine/ Methylene blue/ Safranin/ EosinY/ Phenol red)

Salt and water

Tools:

Compound microscope (single eyepiece)

Dissecting microscope (stereo eyepiece)

Side glass and cover glass for my own sample preparation

A pair of scissors for chopping

Electric scale

A small case to measure the salt and water.

Dissecting kit

Dropper pipette

Tweezers

Lamp

Camera station that is attached to either the light or dissecting microscope

 Procedure: 

1. Rescued the microscopes from inside or under their own box or cover. 

2. Set the lights into the compound microscope, adjusted its focus using the practice slides and saw how it looks like.         

3. Cut the onion into a little piece, and stripped a thin inside skin off.       

4. Put the skin on the slide, dropped 1 or 2 drops of water on it, and covered it by a cover glass.      

5. First just looked at it using the compound microscope without staining it. Tried different objective lenses in this process. 

6.  When I could find the cell walls and nucleus in each one of them, then I took pictures of them using the computer.      

7.      I stained the onion cell with the Methylene blue using the Dropper pipette and observed how it looks like.    

8.      Then next, I cut the sliced potato into very thin, made the slide with it, and observed the slide with the Compound microscope.

9.      I added the EosinY in it, and abserved it again.

10.   I cought water fleas from the plastic micro-centrifuge and made a slide with it carefully putting a cover glass on it.     

11.  Observed the slide with the Compound microscope and took its picture using the computer. 

12.  Observed the fish egg using the Dissecting microscope, and saw how it looks like.      

 

13.  Observed the dragon fly using the Dissecting microscope, and saw how it looks like.

 

14.  Made the onion slide again, observed it without stain it. Then I added the salt water (salt: water= 1:6 g) slowly with the dropper pipette and observed how it changes. 

Results: 

Sample Slide: When I looked at the sample slide, I could see small letter “e” on it.

 

Onion Cell: When I looked at the slide on which I put the onion inner skin, even though I didn't stained it, but I could see its cell walls and nucleus in each one of them.

When I stained the onion cell with the Methylene blue using the Dropper pipette and observed it, I could see the nucleus in each one of the cell walls. 

Potato Cell:  I observed the potapo cell with the Compound microscope, and then I noticed that it looks quite different from the onion cell, because there were a lot of bubbles on or in the each cell wall. 

After this, I added the EosinY on it, and observed it again.

Then I could see the bubbles and cell walls more clearly.

 

Water Fleas: I made a slide with some water fleas and observed how they look like. It looked very much different from plant cells. They didn’t have cell walls, and I could see many small yellowish round things in it. I also could see it’s moving because it was still alive.     

 

Fish Egg: When I observed the fish egg using the Dissecting microscope, I only could see big shiny red fish egg. I couldn’t really see any cells in it.

Dragon Fly: I observed the dragon fly using the Dissecting microscope, and noticed that it is coved by small thin hairs all over its body. I could see the very detail but cell using the dissecting microscope.

 

Plasmolysis: I added the salt water (salt: water= 1:6 g) slowly into the onion slide with the dropper pipette without staining. As soon as I added the saltwater, I could see the change of the plasma membranes. They shrunk very rapidly separating from their cell walls. This change happened within about 20 -30 seconds. I took its video.

Control(Before adding the salt water) 

The result of the plasmolysis (after adding the salt water)  

Conclusions: I could observe many plants and some organic cells using the both compound and dissecting microscopes. I think I could observe cells and biological matter at both the microscopic and macroscopic level. I also could observe some different cell types and the organelles they contain. I could see firsthand the major differences between plant and animal cells. All organisms consist of one or more cells and I used some specific stains to highlight some of the organelles and structures they contain, such as Nucleusｓ. .

Comments/ Discussion: When I looked at the fish egg using the dissecting microscope, I could see the shiny red stuff in it. I remember some students tried to put fish egg into the salt water, I wonder what happened to them after that. I guess that it might be shrunk because of the osmotic pressure.

I have studies about the plasmolysis before at my high school, but I don't remember if once the plasmolysis happened, there is any ways to make it back to the original place or not.

 Answer to Questions: 

1)      If you increase the magnification, what happens to your field of view?

-If I increase the magnification, the field of view decreases.

 

2)      What is the difference between the conventional microscope and the dissecting microscope? Why did you choose the microscope you did for the samples you looked at?

-A dissecting microscope has a lower magnification than a compound microscope. A dissecting microscope has a bigger work area so you can use it to magnify and still move around what ever you’re looking at. A compound microscope would be used to look at cells that you could not see with out intense magnification you would have to use a microscope slide for whatever you wanted to look at.

àExample: A dissecting microscope would be used to figure out the sex of the dragon flies. While a compound would be used if wanted to see the cells of its eye.

3)      What was the most obvious difference between animal cells and plant cells?

Animal cells don't have the cell wall, vacuole and chloroplast but plant cells have all of them.

4)      How and why does plasmolysis occur? What does this have to do with wilting?

   -Plasmolysis is when a cell shrinks due to water leaving. It happens when the

    pressure decreases to the point where the protoplasm of the cell peels away from

       the cell wall, leaving gaps between the cell wall and the membrane.

       When plant lost their water, the cells would also lose their turgidity; therefore the

       plants would wilt in this process. 

 

 

BIO150-3 / Report Lab 1: DNA Extraction

Lab 1: DNA Extraction

 Aim:To isolate DNA from Kiwi fruit and to observe how it looks like. 

 Purpose:To see DNA with my own eyes and understand that it exists in all cells even though it is plant or food. DNA is a major topic in the introduction to Biology lecture course (BIO 100), so being familiar with this molecule is very important. 

Materials: 

¼ Kiwi fruit

2.5g washing up liquid

1g salt

50mL tap water

Ice cold alcohol; isopropanol（put in freezer for at least 30 mins）

Tools:

Knife to cut a kiwi in to ¼

Zip-lock bag for mashing a kiwi in

A pair of scissors for chopping

Major

Pen to label mu name on the bag

A small case to put the materials of extraction buffer and mix them in

Beaker

Centrifuge

Filter paper

Funnel and funnel stand

Bunsen burner

A long glass hook

Clean glass test tube

pH paper

Plastic micro-centrifuge tube

Blue pipetman

Procedure: 

1. Peel the kiwi fruit into 1/4 and chop it into small chunks using scissors.

 

2. Put the chunks in a zip-lock bag and mash the kiwi to break up some of the cells and provide a large surface e area over which to extract the DNA.

 

3. Make the extraction buffer by mixing together the washing up liquid, the salt and the tap water. Stir slowly until the salt has dissolved, not making bubbles.

4. Add the extraction buffer to the mashed up kiwi and mash more to get out DNA at the end.

 

5. Label the bag with my name and incubate the kiwi and extraction buffer mixture at 60 Celsius for 15 min in the water baths. Incubation helps to break up the cells further and starts to degrade some of the cell’s proteins. This is because Kiwi, like some other tropical fruits have special enzymes called proteases which are proteins which cut up or digest other proteins.

 

6. Remove my bag from the water bath and filter the kiwi mixture into a beaker using filter paper, a funnel and a funnel stand. Filtration removes all the unwanted lumps and bits of kiwi fruit ad should leave you with a salty and soapy green liquid: extract which contains the kiwi fruit DNA.
7. Pour some of this extract into a large glass tube and carefully add an equal volume of cold isopropanol from a tube in the freezer by poring it slowly down the side of the jar. The alcohol forms a layer on top of the kiwi extract because it has a lower density. Between the two layers of liquid, there is a white jelly-like substance forming, this is DNA. Then, mix the liquids to make your DNA stick together.

 

8. Make a long glass hook by carefully heating a glass Pasteur pipette in the flame of the Bunsen burner. Then, reach down this hook inside and gently fish out some of the kiwi DNA which is very long and fragile. 

9. One way to show that what you have isolated is DNA, is by checking its pH when dissolved in water.

 

10. Transfer thee fished DNA into a labeled plastic micro-centrifuge tub and pour in some of your unfinished liquid until the rube is almost full. Centrifuging this material for 2 minutes to cause the heavy aggregates of DNA to form a “pellet” in the bottom of the tube. When I put it in the centrifuge, I should balance the tube with another off the same volume to prevent that the centrifuge doesn’t suffer.

 

11. Remove the liquid above the pellet using a pipetman and a blue tip.

 

12. Resuspend the pellet using 1mL of distilled water and a new blue tip.

 

13. Check and record the pH off the DNA solution using Hp paper. Also measure the pH of an appropriate “control”.

 

Results:  Until before I incubate the kiwi and extraction buffer mixture at 60 Celsius for 15 min in the water baths, I couldn’t see any specific changes in the zip-lock bag. After the incubation, I could see the color change. It was light green before but it became yellowish green after the incubation. Therefore after I filtered the kiwi and extraction buffer mixture, I got a clear yellow liquid as I showed below.

 

When I added an equal volume of cold isopropanol into the tube which the filtered the kiwi and extraction buffer mixture in, I quickly could see some changes in it. As I wrote above in the procedure section, the alcohol forms a layer on top of the kiwi extract. Between the two layers of liquid, there is a white jelly-like and tiny bubble-like substance forming,

 

When I fished the DNA using the glass hook, I could feel that the DNA is really like a jelly, sticky and very condensed. After I centrifuged the DNA, it precipitated on the bottom of the micro-centrifuge tube and formed “pellet” there. It didn’t move even though I shook it hard.

 

After I poured the distilled water in the micro-centrifuge tube, the pellet was dissolved. Then, I measured its pH, it was pH 4, means it acid. I also measured the pH of an appropriate control which is the distilled water, it was neutral. Therefore, I can say DNA is acid.  

 

Conclusions: I could actually take DNA out from foods through this process, could see it with my own eyes clearly and understand that it exists in all cells even though it is plant or food.  According to the name of DNA which stands for Deoxyribonucleic acid, it should be acid, in this experiment, I could proof that DNA is acid indeed.  

 

Comments/ Discussion: I could see some differences between my result and some other classmates’ one after the filtering and also after adding the isopropanol. I got clear yellowish liquid after filtering but some others got milky yellowish liquid on the other hand. That was maybe why they couldn’t get the jelly-like DNA. I wonder where these differences came from.

When I measure the extraction buffer by mixing together the washing up liquid, the salt and the tap water, I measured them very carefully and I followed the instruction step by step. Did this make some differences?

 

After we take the DNA out, is there any ways to see the famous spiral form of DNA using the normal microscope somehow?  Since I know that as DNA is so thin, I wouldn’t be able to see it without an incredibly powerful microscope usually, so I wonder if I can see it or not.

 

Answer to Questions:

1), why did we use kiwi as our sample today?

To see DNA with my own eyes and understand that it exists in all cells even though it is plant or food. And also kiwi is soft to mash, and it is a fruit which we all are familiar with.

 

2). what was the washing up liquid for?

It dissolves the fatty cell membranes.

 

3). what did you use for your pH measurement control?

I used the same distilled water which I put into the plastic micro-centrifuge tube with pellet in.

 

4). what happens to the DNA that you eat and does eating modified DNA pose any danger to you?

GM foods are produced by artificially introducing new genes (DNA) into the cells of the organism to be modified. This is often done by a process called transformation in which "naked" DNA is added to cells and the DNA is assimilated by the transformed cells and incorporated into their chromosomes.

Eating modified DNA would pose some dangers to us. Manipulating genes is still under the research and even scientists are not crystal clear about its consequences. It is said that it might generate some unknown allergen or unexpected toxins. Therefore eating the genetically modified food is risky.

 

References:

http://www.newton.dep.anl.gov/askasci/mole00/mole00606.htm

http://www.smalltown.ne.jp/~usata/memo/gmo.shtml#food

http://www.seedsofdeception.com/GMFree/GMODangers/DangersofGMFoods/index.cfm

 

5). What does the term GMO mean?

It means the genetically-modified organisms.

References: http://www.raw-wisdom.com/50harmful.

http://www.newscientist.com/article/dn9921-instant-expert-gm-organisms.html

http://www.ornl.gov/sci/techresources/Human_Genome/elsi/gmfood.shtml