mistake in destroyer

[vj212306]

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Bio section # 237 in destroyer doesnt make sense at all... plz check yall..

Are there more errors in this book??

 

[LNinlove]

Did I get the shaft? My destroyer only goes up to 168...are these the updates I keep hearing about?

 

[whoaaitzkyle]

Did I get the shaft? My destroyer only goes up to 168...are these the updates I keep hearing about?

yes, email Nancy and she will mail them to you. it goes up to 278

 

[whoaaitzkyle]

Bio section # 237 in destroyer doesnt make sense at all... plz check yall..

Are there more errors in this book??

yes, it's a mistake in the book.

 

[Toothguy80]

My destroyer goes up to 213

write out the question here........

 

[poc91nc]

How is it wrong?

2x2x2x2 = 16

There are two from the original strand...

 

[poc91nc]

My destroyer goes up to 213

write out the question here........

You should get in touch w/ Nancy...there are a lot of new questions that have been developed!

 

[poc91nc]

Did I get the shaft? My destroyer only goes up to 168...are these the updates I keep hearing about?

You either purchased a used edition...or you bought it a LONG time ago!

Even in August there were about 198 bio questions.

 

[Speeddater]

yes, email Nancy and she will mail them to you. it goes up to 278

Umm, I purchased the book at the beginning of this month, and the updated edition says April 21, 2007 and I believe there are 268 questions no? I confirmed this with Dantheman2007, and 268 was the latest updates he received. Just making sure, thanks.

 

[vj212306]

How is it wrong?

2x2x2x2 = 16

There are two from the original strand...

The question is: if a DNA is replicated 4 times, how much percent is the original DNA are there?

2 to 4 then to 8 then to 16 then to 32

2/32*100 is 6.25.

 

[poc91nc]

The question is: if a DNA is replicated 4 times, how much percent is the original DNA are there?

2 to 4 then to 8 then to 16 then to 32

2/32*100 is 6.25.

My bad, you're right!

 

[whoaaitzkyle]

I'm sure it goes up to 278 for the bio section. I just got an update from Nancy like 2 weeks ago or so.

 

[Speeddater]

I'm sure it goes up to 278 for the bio section. I just got an update from Nancy like 2 weeks ago or so.

Meant to PM you whoaaitzkyle

 

[litldime]

I'm sure it goes up to 278 for the bio section. I just got an update from Nancy like 2 weeks ago or so.

well i definately need to email her..mine goes up to 268....what do include in the email? is there an order number or something...or do they just look up our names?
thanks
-ld
any updates for anything other than bio?

 

[Dotoday]

The question is: if a DNA is replicated 4 times, how much percent is the original DNA are there?

2 to 4 then to 8 then to 16 then to 32

2/32*100 is 6.25.

Yeah, this question is ambiguous. It needs to be restated. If you do it by the experimental way of Messelson and Stahl then yes you do get 12.5% of original DNA in a Cesium gradient. However, if you do it on a paper with a two strands then you do get 6.25%. Both of the answers are right. However, they need to make up another question.

 

[poc91nc]

I will back up Dotoday. It REALLY REALLY depends on how you look at it!!!

BIOCHEMISTRY 2nd Edition by Donald Voet
Figure 28-7

In this figure you will see a full explanation of the Meselson and Stahl experiment. Voet Biochemistry has the BEST explanation of this experiment.

The figure shows that after 4 rounds of replication, it shows that 1/8 = 12.5% of the DOUBLE STRANDED DNA are hybrid DOUBLE STRANDED DNA strands.

Hybrid meaning, the original strand was composed of a heavy nitrogen isotope.

Thus, the answer really depends on what you define as a UNIT OF DNA.

There are 32 TOTAL strands present....but 16 DOUBLE STRANDS OF DNA UNITS.

 

[poc91nc]

When I first did the problem, I just did 2^4 = 16. That's how I got my answer.

The only thing this problem needs is to be more specific regarding the unit of DNA.

 

[SimSimma]

the question is slightly vague, but its not wrong. the wording in the problem just needs to specify maybe what a dna segment is. but everyone knows that a DNA strand is a double helix, so thats the way i did it.
the best way to do this problem is to draw it out.

 

[hrndawg]

Messelsohn and Stahl's experiment proved that DNA replication is done through a semiconservative approach...This means that when the double stranded helix unwinds during replication, each strand is replicated forming 2 new double helix, each containing 1 strand of the original DNA. Thus after one round of replication, both strands contain original DNA material.

During the second round of replication, these two new strands unwind and the four single strands are used as templates for new double helix. At the end of the second round, there are 4 DNA double helix, with only two of them containing original strand DNA. Similarly the third round produces 8 new DNA double helix, with still only 2 containing the original DNA. After the 4th round, there are a total of 16 DNA double helix, with still only 2 containing the original DNA. That is 2/16=1/8=12.5% There is no mistake and I don't think the question is unclear. Messelsohn and Stahl's semiconservative approach is the accepted theory on how replication works, so the question does not need to explain that this question is working in regards to their theory.

 

[poc91nc]

the question is slightly vague, but its not wrong. the wording in the problem just needs to specify maybe what a dna segment is. but everyone knows that a DNA strand is a double helix, so thats the way i did it.
the best way to do this problem is to draw it out.

Totally agree simsimma! When I first did the problem, I assumed double strand and just did 2^4 and got the right answer.

I guess the lesson is...if you see a question like this make sure to read what defines a unit of DNA (in the question).

 

[Alliekat423]

Here is the same question from a Kaplan practice test....but there is a conflicting answer:

If a strand of DNA underwent four rounds of replication, what percentage of the total DNA present would be comprised of the original DNA molecule?

The correct answer is 6.25 (because here a strand is considered a pair of strands), but 12.5 was an alternative (incorrect) answer choice.

So what do we do if a question is this ambigous (if a "strand" means a single strand or a double strand) and gives us both of these answer choices?

To me, a strand of DNA is one single strand because DNA itself is a double-stranded molecule.

Anyone?

 

[laundry]

Um....the Kaplan question is pretty straightforward...after 4 rounds you have 16 replicons, so that's 32 SINGLE strands, only 2 of which are the original.

So, 2/32= 0.0625....

 

[jdoc04]

I hope the picture turns out. I read this thread yesterday and was confused buy the conflicting answers. So I attempted to draw it out. I then googled Meselson-Stahl experiment and found this website which seem so have like I drew it. So is this correct?? If so then 6.25 looks to be right.
2 Original Single Strands/32 Total Strands or 1 Original Double Strand/16 Total Double Strands.

 

[jdoc04]

here is the website: http://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=genomes.figgrp.8112