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27 Mar 2019

Determine the variables tested in each of the following experiments. If applicable, determine and identify any positive or negative controls. Submit this exercise to your instructor upon completion.

1. A study is being done to test the effects of habitat space on the size of fish populations. Different sized aquariums are set up with six goldfish in each one. Over a period of six months, the fish are fed the same type and amount of food. The aquariums are equally maintained and cleaned throughout the experiment. The temperature of the water is kept constant. At the end of the experiment the number of surviving fish are surveyed. A. Independent Variable: B. Dependent Variable: C. Controls:

2. To determine if the type of agar affects bacterial growth, a scientist cultures E. coli on four different types of agar. Five petri dishes are set up to collect results: ï· One with nutrient agar and E. coli

ï· One with mannitol-salt agar and E. coli

ï· One with MacConkey agar and E. coli

ï· One with LB agar and E. coli

ï· One with nutrient agar but NO E. coli

A. Independent Variable: B. Dependent Variable:

C. Controls:

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Trinidad TremblayLv2

29 Mar 2019

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1. A study is being done to test the affects of habitat space onthe size of fish populations. Different sized aquariums are set upwith six goldfish in each one. Over a period of six months, thefish are fed the same type and amount of food. The aquariums areequally maintained and cleaned throughout the experiment. Thetemperature of the water is kept constant. At the end of theexperiment the number of surviving fish are surveryed

A. Independent Variable:

B. Dependent Variable:

C. Controlled Variables/Constants:

D. Experimental Controls/ Control Groups:

2. To determine if the type of agar affects bacterial growth, ascientist cultures E. coli on four different types of agar. Fivepetri dishes are set up to collect results:

One with nutrient agar and E. coli
One with mannitol-salt agar and E. coli
One with MacConkey agar and E. coli
One with LB agar and E. coli
One with nutrient agar but NO E. coli

All petri dishes received the same volume of agar, and were thesame shape and size. During the experiment, the temperature atwhich the petri dishes were stored, and at the air quality remainedthe same. After one week the amount of bacterial growth wasmeasured.

A. Independent Variable:

B. Dependent Variable:

C. Controlled Variables/ Constants:

D. Experimental Controls/ Control Groups:

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Multiply questions here

Q2. What is the consequence of chromosome inversion on meiosis? (work on a zygote with one normal chromosome and one chromosome with an inversion)

Q3. Search the web or read the textbook. Find a disease that is caused by translocation. What kind of translocation causes the disease?

Q4. Briefly explain how downâs syndrome or other trisomy is generated (3 sentences should be enough for you to explain this clearly)

Q5. I mutated a culture of wild type E. coli cells and wanted to isolate mutants that are unable to synthesize uracil (a nitrogen base in RNA). How can I achieve my goal? (try to finish your answer in 2-3 sentences)

Q6. For the ura- mutant isolated in Q5, I want to convert it to URA+ by transformation. Please tell me how I can achive this transformation with 3 SIMPLE sentences

Q7. What is the difference and relationship between an Hfr cell and an F+ cell?

Q8. I want to set up a mating between an Hfr strain and an F- (ade- his- bio-) strain and detect bio+ recombinant. Please design the experiment for me. (What genotype for Hfr do you need to choose? How will you select your recombinant? etc).

Q9. I want to use phage T2 to transducer the wild type ADE2 gene from the wild type E. coli strain to an ade2- E. coli mutant. How can I do this experimentally? (please briefly describe the approach, not experimental details such as incubation for 10 min, etc).

Q10. We talked about recombination in both eukaryotes and prokaryotes. Are there any differences in these two recombination ? (what are they if there are?)

Q11. Whose (or what) experiment proves that DNA is the genetic material?

Q12. What knowledge did Watson and Crick use in constructing the DNA model?

Q13. How does the double helix model support the three major functions of genetic materials?

Q14. What is the major chemical force that holds DNA and histone together? Hydrogen bonds

Q15. If I label E. coli cells in an N15 medium overnight and chase cells in an N14 medium for 2 generations, what fraction of cells still carry the N15 label?

Q16. If a 1000 kilobase fragment of DNA has five evenly spaced replication origins and DNA polymerase moves at 1 kilobase per second, how many seconds will a cell take to produce two daughter molecules?

Q17. DNA polymerases catalyze the polymerization of nucleotides. Use the formula for enzyme catalyzed reaction (see the example) to describe DNA polymerases. Example: Enzyme Substrate A + substrate B -------------------ï product c + product D Q8. During DNA replication, what is the direction of the growing strand?

Q18. For DNA synthesis in cells, why are there a leading strand and a lagging strand?

Q19. The following is the DNA sequence of a template strand. If the primase begins to synthesize primers from the middle âgâ, what will the primer sequence be? (assuming the primer can be 8 nucleotides long) 5â GACTCTAgGACTCCT 3â

Q20. Both DNA polymerase I and DNA polymerase III synthesize DNA during DNA replication. Please state the different roles they played during DNA replication.

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For Discussion (2-3 paragraphs) â¢ What was the concentration of your pre-diluted NPs? â¢ Determine the effect of NPs on brine shrimp lethality. â¢ Determine the effect of NPs on cell viability. â¢ What is (are) the control(s) in this experiment? What is its purpose? â¢ Based on your data in this lab, what is a safe concentration for brine shrimp Threshold Level of Toxicity (TTL)? â¢ Often indicator species are used to study the overall health of an ecosystem. If you were to study an ecosystem containing brine shrimp, would you use it as an indicator species? Why or Why not? Explain your reasoning. â¢ What possible sources of error were present in this experiment?

Introduction

LD50 is a commonly used term to describe acute toxicity: LD stands for Lethal Dose and 50 is used because the dose could kill 50% of the animals exposed to the chemical. For LD50 tests, the animals are given specific amounts of the chemical, orally, by injection or dermally. The value is then reported along with the method of administration and the type of animal used in the test. LD50 is typically reported in milligrams or grams per kilogram of body weight of the animal. The lower the LD50 is, the higher the toxicity of the chemical would be. This information is always provided in Safety Data Sheet (SDS) of chemicals in the âtoxicity dataâ category. A similar measure, the LC50 is usually used to describe the ecological hazards of chemicals. LC stands for lethal concentration that could kill 50% of the animals after 24-96 hours. This value is always provided in Safety Data Sheet (SDS) of chemicals in the âEcological Dataâ category. In this lab, you will be measuring LC50 or LD50 of iron oxide nanoparticles using brine shrimp. Iron oxide nanoparticles are magnetic. Application of magnetic nanoparticles ranges from magnetic storage media to medical industry where they can be used for targeted drug delivery or as contrast agents in MRI. Thus, measuring environmental and biological toxicity of these nanoparticles is crucial. To test toxicity of any such reagents on small organisms, Daphnia and brine shrimps (also known as Artemia) can be used. Artimia are found in salt lakes around the world. They are important live food for aquarium fish. In this lab, you will use brine shrimp to measure toxicity of the nanoparticles. Trypan blue is a stain used to assess cell viability. It is able to diffuse through cell membranes of dead cells but is unable to permeate live cells. This stain can be used to assess cell survival 1 Fall 2017 following exposure to chemicals, nanoparticles and experimental drugs. The ratio of live: dead cells can be used as a preliminary assessment of cytotoxicity and translated to tissue viability.

Methods Part A: Serial Dilution of NP Solution 1) Label 5 test tubes as 0, 1:1, 1:10, 1:100, 1:1000 2) Add 2mL of seawater to tube 0 3) Add 2mL of specific group stock solution to tube 1:1 and add 2mL of seawater to it. 4) Transfer 1mL of stock solution to tube 1:10 and add 9mL of seawater to this tube 5) Transfer 1mL of 1:10 solution to the tube labeled as 1:100 and add 9mL of seawater to â¨this tube 6) Transfer 1mL of 1:100 solution to the test tube labeled as 1:1000 and add 9mL of â¨seawater to this tube Part B: Preparation of test environments 1) Label 5 wells of 6-well plate as control (0), 1:1, 1:10, 1:100 and 1:1000 2) Label 3 petri dishes as: control (0), 1:1 and 1:1000 â¨NOTE: Be sure to include your initials on all plates 3) Transfer 2mL of each solution from the corresponding test tube to the respective wells on your six-well plate and each petri dish Part C: Preparing specimens for the Trypan blue cell viability test 1) Transfer 2 brine shrimp into each of the pre-labeled petri dishes containing the solution of NPs and seawater (0, 1:1 & 1:1000) and set a timer for 30 minutes. 2) Transfer a single brine shrimp into the unlabeled petri dish with a drop (~50ul) of seawater and use the dissecting microscope to make observations related to the behavior and morphology of untreated brine shrimp.â¨Make observations in lab notebook of all samples Part D: Preparation of specimens for the toxicity assay 1) 2) 3) 4) 5) Add 10 brine shrimp into each well in the 6 -well plate Make observations in lab notebook Using a dissecting microscope (if needed), count the number of brine shrimp in each well (alive shrimps).â¨Record your data in your notebook using the graphic below as a template. Close the plate and store it for next observation.â¨Observations must be done within 24h-96hâ¨Note: There will be times allocated and a sign up paper for observations Part E: Trypan blue viability test 2 Fall 2017 1) Label 3 glass slides to match the petri dishes prepared in Part C. 2) Transfer 1 brine shrimp from each petri dish onto the corresponding slide. â¨Make observations in your lab notebook 3) Add a drop (~60 Î¼l) of PBS on top of each specimen 4) Add 60 Î¼l of Trypan blue to your shrimp and incubate for 1-2 minutes at room â¨temperature. 5) Wick away excess liquid 6) Add 100 Î¼l PBS to sample and observe (while alive!), looking for blue cells, using the â¨dissecting scope â¨Make observations in your lab notebook 7) Label 3 microfuge tubes to align with each sample. 8) Transfer each brine shrimp from the slide into the corresponding microfuge tube 9) Add 50 Î¼l of PBS to the tube and use the mechanical disruption tool to homogenize the â¨sample for ~2 minutes until a cell suspension has been generated. 10) Load 30-50 Î¼l of your sample onto a new glass slide and add a cover slip. 11)Observe the sample on high power and use the scale below to qualitatively assess cytotoxicityâ 0-no blue 1-some blue 2-fairly blue 3-totally blue.