EK BIO Lecture #3 Exam #

[dreamer67]

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54. One strand of an IS element begins with the nucleotide
sequence 5'-ACTGTTAAG-3'. The same strand must end
with the nucleotide sequence:
A. 5'-GAATTGTCA-3'
B. 5'-TGACAATTC-3'
C. 5'-CTTAACAGT-3'
D. 5'-ACTGTTAAG-3'

C is correct. The passage says that the ends of the strands are reverse compliments of each other. The complement
sequence is 5'-TGACAATTC-3'. The reverse of this is 5'-CTTAACAGT-3'.

I don't understand why the answer is C. I thought the answer would be B. The complement of 5'-ACTGTIAAG-3' would be 3'-TGACAATTC-5', so the reverse compliment would be 5'-TGACAATTC-3'. What am I missing?

 

[MShopes]

54. One strand of an IS element begins with the nucleotide
sequence 5'-ACTGTTAAG-3'. The same strand must end
with the nucleotide sequence:
A. 5'-GAATTGTCA-3'
B. 5'-TGACAATTC-3'
C. 5'-CTTAACAGT-3'
D. 5'-ACTGTTAAG-3'

C is correct. The passage says that the ends of the strands are reverse compliments of each other. The complement
sequence is 5'-TGACAATTC-3'. The reverse of this is 5'-CTTAACAGT-3'.

I don't understand why the answer is C. I thought the answer would be B. The complement of 5'-ACTGTIAAG-3' would be 3'-TGACAATTC-5', so the reverse compliment would be 5'-TGACAATTC-3'. What am I missing?

Hey dreamer67, I just did the same exam today...this question might seem tricky but I got it right.

First thing is you have to quickly break the question into parts. First the passage says that at one end, the nucleotide sequence is complementary to the reverse nucleotide sequence of the other end. What you basically did is you got the complementary to the original not reverse nucleotide sequence!!! Notice the word reverse! So first you have to reverse the nucleotide sequence in question to be 5' GAATTGTCA 3'...I did this simply by getting the letters from the right to start on the left. NOw one step down, then you have to find the complemntary to this which should be 5' CTTAACAGT 3' and thus the answer is C. Notice that the 5' and 3 ' don't matter since it is the same strand any ways. So first you had to find the reverse and then see the complementary sequence to that reverse. The passage exactly says one end is complementary to the reverse of the nucleotide sequence at the other end which lead me to do this quick manipulation of letters.

Hope this helps. If you still don't get it, let me know!

 

[MShopes]

by the way what you did is the opposite. You got the complimentary first then the reverse. The passage says is complimentary to the reverse. So you had to reverse first and then find the complimentary. See, wording can get tricky!

 

[dreamer67]

Hey dreamer67, I just did the same exam today...this question might seem tricky but I got it right.

First thing is you have to quickly break the question into parts. First the passage says that at one end, the nucleotide sequence is complementary to the reverse nucleotide sequence of the other end. What you basically did is you got the complementary to the original not reverse nucleotide sequence!!! Notice the word reverse! So first you have to reverse the nucleotide sequence in question to be 5' GAATTGTCA 3'...I did this simply by getting the letters from the right to start on the left. NOw one step down, then you have to find the complemntary to this which should be 5' CTTAACAGT 3' and thus the answer is C. Notice that the 5' and 3 ' don't matter since it is the same strand any ways. So first you had to find the reverse and then see the complementary sequence to that reverse. The passage exactly says one end is complementary to the reverse of the nucleotide sequence at the other end which lead me to do this quick manipulation of letters.

Hope this helps. If you still don't get it, let me know!

Shouldn't the complimentary sequence be 3' CTTAACAGT 5'?

 

[MShopes]

Shouldn't the complimentary sequence be 3' CTTAACAGT 5'?

That would be true if you are getting complementary sequence of another strand. But notice that it is the same strand so it will be the same direction 5' 3'.