DNA study Guide with Answers PDF

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Prepare for a test about DNA. Includes test questions and answers from DNA experiments to the structure of DNA....

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DNA Study Guide ● ● ●

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What is a vaccine made of? ○ It is prepared from killed or weakened disease-causing agents What does virulent mean? ○ It is harmful - disease causing What did Chargaff discover about DNA bases? ○ Amount of Adenine = amount of thymine ○ Amount of guanine = amount of cytosine ○ The amount of adenine and thymine and guanine and cytosine vary between organisms What sugar is found in DNA? ○ Deoxyribose What’s the definition of Deoxyribose? ○ A five carbon sugar in DNA nucleotides What are the subunits that make up DNA called? ○ Nucleotides What three parts make up a nucleotide? ○ Deoxyribose, a phosphate group, and a nitrogen containing base What are the base pairing rules? ○ Chargaff discoveries: A=T and C=G How are the nitrogen base pairs held together? ○ Hydrogen bonds What does the book mean by complementary base pairs? ○ The two strands contain complementary base pairs, because of the strictness of the base pairing rules. What did Franklin and Wilkins discover about the shape of DNA? ○ The DNA molecules are a tightly coiled helix composed of two or three chains of nucleotides What type of research did Franklin do? ○ She used x-ray diffraction to study the structures of molecules. ○ She studied DNA and viruses How did Franklin’s findings help Watson and Crick? ○ They used her findings (Shape of DNA) to make a DNA model What is a double helix? ○ Two strands twisted around each other, like a winding staircase What is DNA replication? ○ The process of making a copy of DNA When does replication occur? ○ During the Synthesis phase of the cell cycle ○ After the double helix unwinds by DNA helicases What are DNA helicases? ○ They are enzymes that unwinds the double helix What are replication forks?

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○ The areas where the double helix separate Why do we need multiple replication forks? ○ It would take too long for our DNA to copy. What are DNA polymerases? ○ They move along each of the DNA strands adding nucleotides to the exposed nitrogen bases, according to the base pairing rules. Forming two new double helixes What checks to see that there are no errors in DNA replication ○ DNA polymerases What do you end up with after replication? ○ 2 identical DNA molecules, each with one original strand If a human strand of DNA had only one replication fork, how long would it take to replicate? ○ 33 days How long does it take (w/ the normal amount of replication forks) for an entire human chromosome to replicate? ○ 8 hours Which bases are purines? ○ Adenine and Guanine Which bases are pyrimidines? ○ Thymine and cytosine What’s the difference between purines and pyrimidines? ○ Pyrimidines are made of a single ring of carbon and nitrogen atoms. Purines are made of two What was the purpose of Griffith’s experiments? ○ He was trying to prepare a vaccine against pneumonia What causes pneumonia? ○ Streptococcus pneumoniae or S. pneumoniae, a prokaryote (bacterium) causes pneumonia. What is the difference between the first strain of pneumonia and second strand that Griffith worked with? ○ The first one is enclosed/protected by a capsule composed of polysaccharides. Which protects the virus from the body’s defense system. The first one also caused the disease when it was grown in the petri dish. ○ The second one did not have the capsule and did not cause the disease when grown in the petri dish. What did Griffith do to determine if the capsule was causing the mice to die? ○ He put a vaccine of heat-killed S bacteria into the mice. ○ They still lived. The capsule was not causing the mice to die What step did Griffith take to discover transformation? ○ He mixed the harmless R bacteria with the harmless heat killed S bacteria. Those mice died.

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He found the R bacteria had acquired capsules. They had become virulent S bacteria. ○ Transformation is a change in genotype caused when cells take up foreign genetic material. What did Avery and his co-workers discover? ○ DNA is responsible for transformation What information allowed Hershey and Chase to begin their experiment? ○ Viruses are composed of DNA or RNA surrounded by a protective protein coat. ○ When phages infect bacterial cells, the phages can produce more viruses, which are released when the bacterial cells rupture. ○ Only molecule in the phage that contains phosphorus is DNA ○ Only phage molecules that contain sulfur are its proteins in its coat What is the definition of a bacteriophage? ○ A virus that infects bacteria What was the first step of Hershey and Chase’s experiment? ○ They grew two phages. Both Escherichia coli (E. coli), however one contained Radioactive sulfur (35^S) and the other contained radioactive phosphorus (32^P) 2nd step? ○ The two phages infected two separate batches of E coli bacteria. ○ Radioactive elements release particles that can be detected by machines, so the scientists could follow it and decide if it was the DNA or the proteins that issued the instructions to the bacteria. 3rd step? ○ The scientists separated the phages from the bacteria uses a blender. ○ They used a centrifuge to separate the bacteria and the phages. The heavier bacterial cells formed a solid layer at the bottom. The lighter viral parts remained in the upper, liquid layer. ○ They examined the bacteriophages What were the results? ○ The 35^S label was still part of the phage - the protein was not injected into the bacteria ○ The 32^P label was in the lower layer. The DNA had been injected into the hosts. What did they conclude from this? ○ DNA is the hereditary material in viruses...