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#1
06-19-2012
 USMLE Forums Master Steps History: 1+CK+CS Posts: 1,039 Threads: 189 Thanked 570 Times in 323 Posts Reputation: 580
A sample DNA has...

A sample DNA has 10% A and 50% G. Which of the following statements is true:

A) This DNA has 10% T
B) This DNA has 10% U
C) This DNA has 50% C
D) This DNA could be a single stranded viral DNA
E) This DNA could be a double stranded viral DNA

#2
06-19-2012
 USMLE Forums Master Steps History: 1+CK+CS+3 Posts: 791 Threads: 76 Thanked 673 Times in 317 Posts Reputation: 691

its D....SINGLE STRANDED DNA.....this question is from kaplan notes right?????
#3
06-19-2012
 USMLE Forums Master Steps History: 1+CK+CS Posts: 1,039 Threads: 189 Thanked 570 Times in 323 Posts Reputation: 580
:)

Quote:
 Originally Posted by anomali its D....SINGLE STRANDED DNA.....this question is from kaplan notes right?????
I will post correct answer and the source in a couple of hours. Please be patient - I want other people to have a chance to answer the question without a spoiler Thanks

#4
06-19-2012
 USMLE Forums Addict Steps History: Not yet Posts: 125 Threads: 17 Thanked 67 Times in 38 Posts Reputation: 77

chargaff's rules-%A=%T(%U ),%G=%C,%PURINES=%PYRIMIDINES IN DOUBLE -STRANDED DNA OR dsRNA (%U)
so by these rule if A IS 10% T SHOULD BE 10% AND %G+%C=100%-(10%+10%), 40%C AND 40%G ,SO DNA IS SINGLE-STRANDED
 The above post was thanked by: numbndumb (06-20-2012)
#5
06-20-2012
 USMLE Forums Master Steps History: 1+CK+CS+3 Posts: 529 Threads: 57 Thanked 284 Times in 152 Posts Reputation: 294

yup, its d for sure
__________________
I've become so numb
#6
06-20-2012
 USMLE Forums Master Steps History: 1+CK+CS Posts: 1,039 Threads: 189 Thanked 570 Times in 323 Posts Reputation: 580

Correct answer id D) This DNA could be a single stranded viral DNA

Just a quick reminder: From calculation we can see that Chargaff's rule (% of A=T/U, % of C=G) doesn't apply here. And this rule applies to double-stranded DNA only.
So presented DNA can be a single-stranded DNA/RNA, viral or any other..

The question was based on what they talk about in Kaplan videos

Last edited by Casandra; 06-20-2012 at 08:42 AM.
 The above post was thanked by: dockhi (06-20-2012)
#7
06-20-2012
 USMLE Forums Guru Steps History: 1+CK+CS Posts: 307 Threads: 36 Thanked 127 Times in 61 Posts Reputation: 137

It can't be E solely because the rule applies to double stranded DNA?
I'm forgetting such simple concepts
#8
06-20-2012
 USMLE Forums Master Steps History: 1+CK+CS Posts: 1,039 Threads: 189 Thanked 570 Times in 323 Posts Reputation: 580
.

Quote:
 Originally Posted by dockhi It can't be E solely because the rule applies to double stranded DNA? I'm forgetting such simple concepts

correction form my side - the rule applies to double-stranded DNA and RNA.

In the previous post I was referring to that specific case where we had DNA. I meant only ds-, not only DNA.
 The above post was thanked by: dockhi (06-20-2012)

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