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  #1  
Old 06-13-2011
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DNA This is the codon, what will be the mRNA!

The codon for a gene is : CAGCGC, what is the sequence of mRNA upon transcription of this gene?

1, GCGCTG
2, CUGCGC
3, GCGCUG
4, CAGCGC
5, GUCGCG

Last edited by usluipek; 06-13-2011 at 01:49 PM.
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  #2  
Old 06-13-2011
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Any thought on this?
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  #3  
Old 06-13-2011
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Well if the gene sequence you have given is 5'--> 3' (which we have to assume), then the mRNA sequence should be the same as the gene sequence with T's replaced by U's.

Since there are no T's, the mRNA should read the same as the gene, GAGCGC, but this is not an answer choice.

And I'm not sure what you mean by "codon of a gene." It should be gene sequence. A codon is located on mRNA
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Old 06-13-2011
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Quote:
Originally Posted by apx85 View Post
Well if the gene sequence you have given is 5'--> 3' (which we have to assume), then the mRNA sequence should be the same as the gene sequence with T's replaced by U's.

Since there are no T's, the mRNA should read the same as the gene, GAGCGC, but this is not an answer choice.

And I'm not sure what you mean by "codon of a gene." It should be gene sequence. A codon is located on mRNA
ya, you are rite
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Quote:
Originally Posted by leo lakhani View Post
ya, you are rite
3. is the answer...wats th eanswer?
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  #6  
Old 06-13-2011
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DNA 5' - 3': CAGCGC
mRNA should be: GCGCUG

So, #3 is my answer, but the book says #4

Last edited by usluipek; 06-13-2011 at 01:50 PM.
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Old 06-13-2011
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Do you have the explanation?
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The book does not have explanation for the answer. Just the answer. I am puzzled, could it be a typo?
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Quote:
Originally Posted by usluipek View Post
DNA 5' - 3': CAGCGC
mRNA should be: GCGCUG

So, #3 is my answer, but the book says #4
Remember that DNA is read 3'-->5' so whenever a gene sequence is given 5'-->3' we can safely assume that it is the coding strand.

So the mRNA will be the same as the gene sequence written 5'-->3' except with U's instead of T's

The 5'-->3' strand is always the coding strand; the 3'-->5' strand is the template strand
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I agree with apx.....the answer is 3 by my standards as well....I'm pretty sure the book is wrong

great explanation apx! but yes whatever apx said is right, you have to assume that they gave the original sequence from 5'-3' and since transcription reads 3-5 and makes mRna 5-3 this means that the original 5'-3' is read "3'-5' " and now copied with U's instead of T's (cuz its Rna)...

Correction.....coding strand = mRNA

Last edited by Dr_Kal_El; 06-13-2011 at 09:05 PM.
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  #11  
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Option 4 CAGCGC is the answer, codon of a Gene is the same as the strand that will be codified (Codification strand)
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book is right
its answer 4

coding strand of DNA is
5`CAGCGC 3`

template strand will be

5`GCGCTG 3`

then mRNA strand is

5`CAGCGC 3`

as far as i know tahts it..plz correct me here too if its wrong...
Molecular biology ....transcription
(plz see question number 2 and make me correct there too)...
thanks..

Last edited by INCOGNITO; 06-13-2011 at 08:12 PM.
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Default i think it's 4 too

Quote:
Originally Posted by usluipek View Post
The codon for a gene is : CAGCGC, what is the sequence of mRNA upon transcription of this gene?

1, GCGCTG
2, CUGCGC
3, GCGCUG
4, CAGCGC
5, GUCGCG
cuz i think in any given question unless they are telling u the 5'and 3'
u have to assume that this strand is 5'------>3' and since u need to make a mRNA
Then u have to transcrib it twice on for the complementery double strand and one for the mRNA which is going to be a mirror image of the 5' ---->3'
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Quote:
Originally Posted by mmtj View Post
cuz i think in any given question unless they are telling u the 5'and 3'
u have to assume that this strand is 5'------>3' and since u need to make a mRNA
Then u have to transcrib it twice on for the complementery double strand and one for the mRNA which is going to be a mirror image of the 5' ---->3'

ok. so does that mean that whenever they give a genetic code it is for the coding strand? and not the template strand.???really confusing......
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Default option 4

I will go with the option no 4 because its codon not a template. codon and mrna has same sequence except T for U in mrna. Here we are talking about codon not template so it wont be antiparallel and complimentary.
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  #16  
Old 06-14-2011
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Default Answer is 4

Although the mRNA is transcribed using the template strand , the mRNA represents the coding strand {complementary base pairing , with the exception of T= U on the mRNA }, and when not mentioned its arbitrary to read the code in 5' to 3' i hope this explains
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