Submit reasoning and process, not merely answers! Problem Set 4: DNA Structure a

Question

Submit reasoning and process, not merely answers!

Problem Set 4: DNA Structure and Replication Submit reasoning and process, not merely answers! 1. You work at the Center for Disease Control and have been given to analyze a suspected bioterror agent that may be a type of Variola, a double-stranded DNA virus that is the causative agent of smallpox. Smallpox was one of humanities major scourges, killing as many as 500 million people in the 20h century. It is believed to have been wiped out in 1979 with arn aggressive vaccination campaign. Since few alive today are resistant to smallpox, a live virus could wreak havoc To analyze the virus, you obtain DNA from the precious sample of purified virus and (asa control) from canine parvovirus, a single-stranded DNA virus you happen to have on hand Unfortunately, you forget to label the two tubes! What else to do but to continue. so you analyze the two DNA samples for nucleotide composition (in the same way as Chargaff) giving the results shown below. Which tube contains which Variola DNA, and why? Recovery 93.2 94.1 Tube 1 15.7 33.4 32.7 11.4 Tube 2 18.7 34.4 26.9

Explanation / Answer

ANSWER 1.

According to Chargaff’s Rule in Double strand DNA the amount of adenine (A) is equal to the amount of thymine (T). Similarly the amount of adenine (A) is equal to the amount of thymine (T).

i.e. Amount of Purine is equal to amount Pyrimidine.

Tube 1 contains bases of Variola DNA (double stranded DNA).

In tube 1, percentage of A and T is nearly same and percentage of G and C also nearly same. DNA in tube 1 seems to follow Chargaff’s rule, so this contains double stranded DNA. Tube 1 contains bases of Variola DNA as we know its DNA is Double-stranded DNA.

Bases in Tube 2 are not according to the Chargaff’s rule. We know Single strand DNA not follows the Chargaff’s rule. Canine parvovirus is Single-stranded DNA virus so tube 2 contains bases of parvovirus.

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