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

As per above information,

Variola virus is a double stranded DNA molecule and Canine parvovirus is a single stranded DNA molecule.

Now one tube consists of double stranded DNA which is variola virus and other must contain single stranded DNA which is canine parvovirus.

It is clear that variola virus DNA follows chargaff's rule of A+T = C+G or in other words we can say,

A : T = 1 and G:C = 1.While single stranded DNA will not follow chargaff's rule.

In case of single stranded DNA ,

the adenine(A) to thymine(T) ratio is approximately equals to 0.77 and guanine(G) to cytosine(C) ratio is approximately equals to 1.3.

Here in case of

Tube 1

A : T ratio = approximately 1

G : C ratio = 1.3 (this variation is because of the recovery percentage which is not 100%)

while in Tube 2

A : T ratio = approximately 0.78

Ratio of G : C = 1.3

Tube 2 follows the single stranded DNA characteristics while Tube 1 follows double stranded DNA characteristics clearly in case of thymine and adenine ratio.

Some variation or accurate values of ratio are not seen because of the recovery percentage.

So Tube 1 contains double stranded DNA molecule i.e variola virus as it follows chargaff's rule. (clearly in case of A : T)

Related Questions

Navigate

• Browse (All)
• Browse S
• Subjects

---