Does it matter which strand is the 'code strand'? The following two sequences look identical, except one runs 3'-5' and the other 5'-3'. For each DNA sequence given below, write the mRNA sequence that would be coded from it. Make sure you indicate the direction of each mRNA strand (i.e. 3' and 5' ends).
a. DNA 3'-TACCTACTTTGCCCGATCCAT-5'
mRNA
b. DNA 5'-TACCTACTTTGCCCGATCCAT-3'
mRNA
A - 5-3
UACCUACUUUGCGCGTAUCCAT
B - 3-5
UACCUACUUUGCCCGAUCCAU
To find the mRNA sequence coded from a DNA sequence, you need to identify the complementary DNA strand and then replace the T's with U's in the mRNA sequence.
In the given DNA sequence:
a. DNA 3'-TACCTACTTTGCCCGATCCAT-5'
The complementary DNA strand would be:
5'-ATGGATCGGGCAAAGTAGGTA-3'
Replacing the T's with U's, the mRNA sequence would be:
5'-AUGGAUCGGGCAAAGUAGGUA-3'
Therefore, the mRNA sequence for the given DNA sequence is 5'-AUGGAUCGGGCAAAGUAGGUA-3', with the direction indicated as 5' to 3'.
b. DNA 5'-TACCTACTTTGCCCGATCCAT-3'
The complementary DNA strand would be:
3'-ATGGATCGGGCAAAGTAGGTA-5'
Replacing the T's with U's, the mRNA sequence would be:
3'-AUGGAUCGGGCAAAGUAGGUA-5'
However, while this is the correct mRNA sequence, the direction is indicated as 3' to 5'. To convert it to the 5' to 3' direction, we need to reverse the sequence:
5'-AUGGAUCGGGCAAAGUAGGUA-3'
Therefore, the mRNA sequence for this DNA strand is 5'-AUGGAUCGGGCAAAGUAGGUA-3', with the direction indicated as 5' to 3'.