Question 6. DNA structure and function, 5 points The virus \"T2 phage is compose

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Question 6. DNA structure and function, 5 points The virus "T2 phage is composed of two types of macromolecules, DNA and Protein. When this virus infects bacteria, it instructs the bacteria to make many new copies of the phage, resulting in 100s of new T2 phage. Thus, T2 phage must have hereditary material." In a classic experiment in the 1950's two scientists, Martha Chase and Alfred Hershey, used biochemistry to determine if the hereditary material in T2 was DNA or Protein. In one experiment they created T2 phage with labeled DNA by growing the phage in radioactive phosphorus, 37p A. 2 points. What part of the DNA structure did this end up labeling? Add arrows to this diagram to indicate the location of the structure you listed above. B. 1 point In the second lecture we discussed using an enzyme called Ligase. What part f the structure of DNA does it ligate together? C. 1 point. New strands of DNA and RNA set synthesized in nature from 5. 3, what is the functional group at the 3' end that is used for making a covalent bond with the next added nucleotide? D. 1 point. Below is a diagram of a free nucleotide. Which part of this nucleotide would get added to the 3 end of a growing strand of DNA. Indicate your answer circling the atom in the nucleotide below that would covalently bonded to the 3 end of an existing strand of DNA Deoxynucleotide (dNTP) CH Base 0 OH E. ONE EXTRA CREDIT POINT: label the sugar carbons (1-5) on the nucleotide above. F. ONE EXTRA CREDIT POINT: What was the conclusion of the famous "Hershey-Chase experiment, and what was the experimental justification for their conclusion? just look it up in the textbook or online!).

Explanation / Answer

A. Phosphate is part of the DNA nucleotides. The phosphate groups forms the phosphodiester bonds connecting the adjacent nucleotides. This is the region that will be labelled. This is because the viral protein coat is not going to enter the cell but only the nucleotide which will bind with the DNA of the bacteria. This DNA will direct the bacteria to make viral protein coat and there will be new sulphur protein coats. Hence the labelled sulphur from the original T2 phage will not be available or used to make new viral protein coats.

B. Ligase is the enzyme that joins broken DNA strands by mediating the formation of phosphodiester bonds. This plays a role in bringing together the 3' hydroxyl group and the 5' phosphate group close enough to form the phosphodiester bond. This covalent bond formation requires the use of energy as ATP.

C. The phosphodiester bonds is made by the binding of 3' hydroxyl group to the 5' phosphate group of two adjacent nucleotides. Both are the carbon numbers and the functional group found in the 3' carbon of the ribose sugar is the hydroxyl group which releases the proton.

D. The 5' Phosphate group in this free nucleotide is the one that will bind to the 3' hydroxyl group. The first phosphate is the one, alpha phosphate group, and the one nearest to the 5' carbon atom of the ribose sugar, will be the one which will bind to the hydroxyl 3' end of the nucleotide in the DNA strand. This will release a pyrophosphate group.

E. The sugar carbon atoms are numbered clockwise. So the one on the right side of the Oxygen atom will the 1' C, the next 2'C, and the one with the red hydroxyl group is the 3' C, the next near to the Oxygen atom is the 4'C. The methyl group attached to the 4'C is the 5'C and has the triphosphate group extending.

F. The famous conclusion of the Hershey-Chase experiment is that DNA is the genetic material and is the one that binds to the bacterial genome directing the bacteria to synthesize the viral protein coats. They used radiolabelled Sulphur for tagging the viral protein coat and Phosphour for tagging the DNA. The viral protein coat in the progeny had no radiolabelled sulphur and this proves this was not transmitted or carried to the next generation. This was synthesised altogether new coats. The DNA was carrying the labelled protein coat as the DNA is replicated and genetically inherited thus making it the genetic material.

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