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Post by Miss DiFederico on Apr 6, 2012 8:22:55 GMT -5
Here you can create your own practice test questions. Please post the question and the answer so your classmates can practice.
If I see everyone using this folder, I will post practice questions as well. Keep in mind, I am making up your test.
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seema
New Member
Posts: 15
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Post by seema on Apr 12, 2012 19:49:55 GMT -5
Question:
Describe using what we know of DNA structure why most organisms cannot survive in heat and provide an example of the effect of heat.
Answer:
DNA is a long polymer made up of nucleotide monomers where each nucleotide has a nitrogenous base off of carbon 5. Nitrogenous bases include pyrimidines: cytosine and thymine, and purines: adenine and guanine. These bases are an important part of DNA structure because they are essentially what hold two strands of DNA together (DNA is double stranded). Cytosine forms 3 hydrogen bonds with guanine, and adenine forms 2 hydrogen bonds with thymine (complementary base pairing).
Hydrogen bonds however are weak as they are only intermolecular forces, and can be broken down easily when exposed to heat. If an organism was exposed to extreme hot temperatures, the hydrogen bonds holding the 2 strands of DNA together would break apart, thus, would be in high risk. And example of the effect of heat is a sunburn.
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Wondeful answer!!
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Post by Miss DiFederico on Apr 12, 2012 21:35:54 GMT -5
This scientist discovered a substance in the nucleus which did not behave like protein. He called it nuclein.
a) Hammerling
b) Miescher
c) Griffith
d) Chase
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Post by Carly Files on Apr 14, 2012 14:32:44 GMT -5
1)What is associated with only the lagging strand during DNA replication?
-Okazaki fragments
2)Which takes longer to replicate, the discontinuous or continuous strand?
-Discontinuous
3)Which enzyme builds RNA primers?
-Primase
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Post by melanie on Apr 14, 2012 15:19:17 GMT -5
Hii everyone here are some questions I've been thinking of: What were the 3 models of replication that were hypothesized ? -Conservative, Semi conservative, Dispersive Whose experiment helped to determine how DNA replicate and what was the conclusion made? - Meselson and Stahl used Escherichia bacteria and isotopes of nitrogen in an experiment that determined that DNA replicate semiconservatively. Why did Meselson and Stahl use nitrogen? Nitrogen is already a component of DNA found in the nitrogenous bases. Isotopes of nitrogen can be incorporated in the DNA What are Okazaki fragments? -short fregments of DNA that are the result of synthesizing the lagging strand during DNA replication What is the meaning/ importance of complementary base pairing? Complementary base pairing is the pairing of nitrogenous bases between two strands of DNA. ( A-T, C-G) If you know the sequence of one strand you also know the sequence on the complementary strand Whose chemical data accounts for complementary base pairing? Chargaff's chemical data proves this Can adenine bond with guanine? why or why not? Adenine can't bond with guanine for two main reasons: -if a purine and a purine bonded together the DNA molecule will be wider at some points than evidence from x-ray crystallography suggests it should be ( xray diffraction shows that the diameter of DNA should be a constant 2nm) - if adenine formed a hydrogen bond with guanine the resulting molecule will be unstable because of lack of hydrogen bonding -happy studying  |
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Post by Miss DiFederico on Apr 14, 2012 16:24:07 GMT -5
What were the results of the Hershey/Chase experiment?
a) radioactive sulfur was found inside of bacterial cells proving protein is the hereditary material
b) radioactive sulfur was found inside of the bacterial cells proving DNA is the hereditary material
c) radioactive phosphorous was found inside of the bacterial cells proving protein is the hereditary material
d) radioactive phosphorous was found inside of the bacterial cells proving DNA is the hereditary material
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Post by melanie on Apr 14, 2012 21:21:46 GMT -5
What would happen if the DNA gyrase enzyme was not present?
- DNA gyrase is necessary to relieve tension brought about by the unwinding of DNA during replication. It works by cutting both strands of DNA and allowing them to swivel around one another. If the enzyme was not present there would be to much tension in the DNA and it would not be able to replicate properly
..- questions similar to this one explaining why every enzyme in DNA replication is necessary and the consequences that can result if an enzyme is missing or denatured would also be good practice ( i think)
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Post by anjali on Apr 15, 2012 15:51:54 GMT -5
Which of the following is not a nitrogeneous base found in DNA?
a) Cysteine
b) Guanine
c) Adenine
d) Thymine
a) Cysteine is not a nitrogeneous base; it is an amino acid. The nitrogeneous base is Cytosine.
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seema
New Member
Posts: 15
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Post by seema on Apr 15, 2012 17:43:51 GMT -5
Question:
Describe the purpose of DNA gyrase and why it is necessary during DNA replication.
Answer:
DNA gyrase is an enzyme involved in DNA replication which relieves the tension in the double helical DNA caused by unwinding (DNA helicase). DNA gyrase is necessary because without it, the DNA strand that is still in tact may experience too much pressure and stress from the unwinding, causing it to break and halt DNA replication altogether.
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seema
New Member
Posts: 15
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Post by seema on Apr 15, 2012 17:52:30 GMT -5
DNA is a very long molecule. How can it replicate quickly?
a) Enzymes are the biological catalysts that make it replicate faster
b) The warmer the temperature, the quicker it can replicate
c) When two replication forks come close together to produce a replication bubble
d) When DNA Polymerase III and DNA Polymerase I work faster
Answer: C
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Post by Lisa Kim on Apr 15, 2012 19:40:08 GMT -5
What does semiconservative mean?
It means that intermediate band showed that it consisted of strands of two different densities. Also, the interemediate band never disappeared after numerous replications, suggesting that the initial DNA containing 15N continued to exist and to be replicated, so that a heavy strand was always paired with a new light strand (14N)
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Post by melanie on Apr 15, 2012 19:47:40 GMT -5
What does DNA runs antiparallel mean?
This means that the 5' phosphate of one DNA strand is directly across from the 3' -OH of an adjacent strand. In other words while one strand runs from 5' - 3' the other strand will run from 3'-5'
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Post by melanie on Apr 15, 2012 19:49:33 GMT -5
Describe the basic structure of a nucleotide?
A nucleotide consists of a sugar, phosphate group, and nitrogenous base (adenine, thymine, guanine, cytosine)
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Post by melanie on Apr 15, 2012 19:51:25 GMT -5
The bond formed between the 5' C of one nucleotide and the 3' C of another nucleotide is called what?:
a.) phosphodiester
b.) glycosol
c.) phosphodiether
d.) hydrogen bond
Answer: A
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Post by mcramm on Apr 15, 2012 20:19:28 GMT -5
Using the enzymes we know about give a step by step walk through of DNA replication using the enzymes and what their jobs are.
-DNA helicase attaches to the polymer and begins to unzip the two strands
-while this is happening the DNA gyrase relieves the pressure on the other part of the DNA where stress is building (two strings model)
-as the DNA un attaches Single Strand binding proteins come into stop the 2 strands from re-bonding
-RNA primer attaches to the DNA in places where replication must occur, then DNA polymerase III is attracted to the RNA polymer and controls to building on the new DNA
-once replication is complete DNA polymerase I comes in and removes the RNA and replaces it with DNA
-finally the DNA ligase cause the 2 strands the bond and DNA replication is complete
Great question!
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