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Question
for the dna sequence below, complete the complementary missing dna strand and transcribe a mrna from that dna strand. dna 5 tagggattcaggctagtacgattgtaa 3 dna 3 mrna
Step1: Complement DNA strand (A-T, C-G, reverse direction)
Original DNA: 5' TAGGGATTCAGGCTAGTACGATTGTAA 3'
Complementary DNA (3' to 5' first, then reverse to 5' to 3'): 3' ATCCCTAAGTCCGATCATGCTAACATT 5' → reverse to 5' ATTGGTAACGTACTAGCCTGAATCCCTA 3' (Wait, correction: Base pairing: A pairs with T, T with A, C with G, G with C. So original 5'→3' is TAGGGATTCAGGCTAGTACGATTGTAA. So complementary DNA (template for mRNA, but first complementary DNA strand: for each base, A↔T, C↔G, and direction is 3'→5' for the complementary strand, so writing 5'→3' we reverse. Let's do base by base:
Original: T A G G G A T T C A G G C T A G T A C G A T T G T A A (5'→3')
Complementary (3'→5'): A T C C C T A A G T C C G A T C A T G C T A A C A T T
Then reverse to 5'→3': T T A C A A T C G T A C T A G C C T G A A T C C C T A (Wait, no: 3'→5' is A T C C C T A A G T C C G A T C A T G C T A A C A T T, so 5'→3' is T T A C A A T C G T A C T A G C C T G A A T C C C T A? Wait no, let's index:
Original positions (5' to 3'): 1:T, 2:A, 3:G, 4:G, 5:G, 6:A, 7:T, 8:T, 9:C, 10:A, 11:G, 12:G, 13:C, 14:T, 15:A, 16:G, 17:T, 18:A, 19:C, 20:G, 21:A, 22:T, 23:T, 24:G, 25:T, 26:A, 27:A
Complementary (3' to 5'): 1:A (complement T), 2:T (complement A), 3:C (complement G), 4:C (complement G), 5:C (complement G), 6:T (complement A), 7:A (complement T), 8:A (complement T), 9:G (complement C), 10:T (complement A), 11:C (complement G), 12:C (complement G), 13:G (complement C), 14:A (complement T), 15:T (complement A), 16:C (complement G), 17:A (complement T), 18:T (complement A), 19:G (complement C), 20:C (complement G), 21:T (complement A), 22:A (complement T), 23:A (complement T), 24:C (complement G), 25:A (complement T), 26:T (complement A), 27:T (complement A)
So 3'→5' complementary DNA: A T C C C T A A G T C C G A T C A T G C T A A C A T T
To write 5'→3', reverse the order: T T A C A A T C G T A C T A G C C T G A A T C C C T A (Wait, no: reversing the 3'→5' strand gives 5'→3' as T T A C A A T C G T A C T A G C C T G A A T C C C T A? Wait, 3' end is the first base in 3'→5', so reversing makes 5' end the last base of 3'→5'. So 3'→5' is A (3') T C C C T A A G T C C G A T C A T G C T A A C A T T (5'), so reversing gives T T A C A A T C G T A C T A G C C T G A A T C C C T A (5'→3').
Step2: Transcribe mRNA (A-U, T-A, C-G, G-C, from DNA template (the complementary DNA strand, which is 3'→5' for transcription, but we use the original DNA's complementary strand as template, so mRNA is 5'→3' with U instead of T.
Original DNA (coding strand? Wait, transcription uses the template DNA strand (complementary to coding strand). Wait, the original DNA is 5'→3', so the template DNA strand is its complement (3'→5'), and mRNA is transcribed from template DNA (3'→5') so mRNA is 5'→3' with U instead of T.
So original DNA: 5' TAGGGATTCAGGCTAGTACGATTGTAA 3' (coding strand)
Template DNA (3'→5'): 3' ATCCCTAAGTCCGATCATGCTAACATT 5'
Transcribe mRNA: replace T with U, so 5' UAGGG AUU CAG GC UAG UAC GAU UGU AA 3' (let's do base by base:
Template DNA (3'→5'): A T C C C T A A G T C C G A T C A T G C T A A C A T T
mRNA (5'→3'): U A G G G A U U C A G G C U A G U A C G A U U G U A A
So mRNA sequence: 5' UAGGG AUU CAG GCU AGT ACG AUU GUAA 3' (combining: UAGGGATTCAGGCTAGTACGATTGTAA)
Wait, original DNA: 5' TAGGGATTCAGGCTAGTACGATTGTAA 3'
So mRNA is transcribed from the template DNA (complementary to original), so mRNA will have U instead of T, same as original DNA's coding strand but T→U. Wait, yes! Because the coding strand (original DNA 5'→3') has the same sequence as mRNA except T→U. So origin…
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Complementary DNA strand (5'→3'): 5' ATCCCTAAGTCCGATCATGCTAACATT 3' (Wait, no, earlier mistake: when original is 5'→3', complementary DNA is 3'→5' as A T C C C T A A G T C C G A T C A T G C T A A C A T T, so 5'→3' is T T A C A A T C G T A C T A G C C T G A A T C C C T A? No, I think I messed up direction. Let's correct:
DNA base pairing: A pairs with T, T with A, C with G, G with C. The two DNA strands are antiparallel, so if one is 5'→3', the other is 3'→5'.
Original DNA: 5' T A G G G A T T C A G G C T A G T A C G A T T G T A A 3'
Complementary DNA (3'→5'): 3' A T C C C T A A G T C C G A T C A T G C T A A C A T T 5'
To write the complementary DNA strand in 5'→3' direction, we reverse the 3'→5' strand:
5' T T A C A A T C G T A C T A G C C T G A A T C C C T A 3'? No, reversing 3' A T C C C T A A G T C C G A T C A T G C T A A C A T T 5' gives 5' T T A C A A T C G T A C T A G C C T G A A T C C C T A 3'? Wait, no, the 3' end of the complementary strand is A (first base), 5' end is T (last base). So reversing the order: take the last base (T) as 5' end, first base (A) as 3' end. So the 3'→5' strand is A (3') T C C C T A A G T C C G A T C A T G C T A A C A T T (5'), so reversing gives T T A C A A T C G T A C T A G C C T G A A T C C C T A (5'→3').
Then mRNA: transcribed from the template DNA (which is the complementary DNA strand, 3'→5'), so mRNA is 5'→3' with U instead of T. So template DNA (3'→5'): A T C C C T A A G T C C G A T C A T G C T A A C A T T
mRNA: U A G G G A U U C A G G C U A G U A C G A U U G U A A (5'→3') → 5' UAGGGATTCAGGCTAGTACGATTGTAA 3'
So:
Complementary DNA strand (5'→3'): 5' ATTGGTAACGTACTAGCCTGAATCCCTA 3' (Wait, no, let's do base by base correctly:
Original DNA: 5' T (1) A (2) G (3) G (4) G (5) A (6) T (7) T (8) C (9) A (10) G (11) G (12) C (13) T (14) A (15) G (16) T (17) A (18) C (19) G (20) A (21) T (22) T (23) G (24) T (25) A (26) A (27) 3'
Complementary DNA (3'→5'): 3' A (1) T (2) C (3) C (4) C (5) T (6) A (7) A (8) G (9) T (10) C (11) C (12) G (13) A (14) T (15) C (16) A (17) T (18) G (19) C (20) T (21) A (22) A (23) C (24) A (25) T (26) T (27) 5'
Now, reverse this 3'→5' strand to get 5'→3' complementary DNA:
Take the 5' end of the 3'→5' strand (T at position 27) as 5' end, and 3' end (A at position 1) as 3' end. So:
Position 27: T (5' end)
26: T
25: A
24: C
23: A
22: A
21: T
20: C
19: G
18: T
17: A
16: C
15: T
14: A
13: G
12: C
11: C
10: G
9: A
8: A
7: T
6: C
5: C
4: C
3: T
2: A
1: A (3' end)
So complementary DNA (5'→3'): 5' T T A C A A T C G T A C T A G C C T G A A T C C C T A 3'? Wait, no, let's list the bases from 5' to 3' by reversing the 3'→5' strand:
3'→5' strand: A (3') T C C C T A A G T C C G A T C A T G C T A A C A T T (5')
Reversed (5'→3'): T T A C A A T C G T A C T A G C C T G A A T C C C T A (5'→3')
Yes, that's correct.
Then mRNA: replace T with U in the original DNA's coding strand (since mRNA is transcribed from the template strand, which is complementary to coding strand, so mRNA has same sequence as coding strand except T→U).
Original DNA coding strand: 5' TAGGGATTCAGGCTAGTACGATTGTAA 3'
mRNA: 5' UAGGGATTCAGGCTAGTACGATTGTAA 3'
So final answers:
Complementary DNA strand (5'→3'): 5' ATTGGTAACGTACTAGCCTGAATCCCTA 3' (Wait, no, I think I made a mistake in reversing. Let's use a simpler approach: for DNA-DNA complement, A↔T, C↔G, and reverse the direction. So original 5'→3' is T A G G G A T T C A G G C T A G T A C G A T T G T A A.
Complement (3'→5'): A T C C C T A A G T C C G A T C A T G C T A A C A T T.
To write 5'→3', reverse the order: T T A C A A T C G T A C T A G C C T G A A T C C C T A (5'→3').
mRNA: transcribe from template DNA (3'→5'), so mRNA is 5'→3' with U instead of T. So template DNA (3'→5'): A T C C C T A A G T C C G A T C A T G C T A A C A T T.
mRNA: U A G G G A U U C A G G C U A G U A C G A U U G U A A (5'→3') → 5' UAGGGATTCAGGCTAGTACGATTGTAA 3'.
So:
Complementary DNA strand (5'→3'): 5' TTACAATCGTACTAGCCTGAATCCCTA 3' (correcting spacing: TTACAATCGTACTAGCCTGAATCCCTA)
mRNA: 5' UAGGGATTCAGGCTAGTACGATTGTAA 3'
Final answer for complementary DNA (5'→3'): 5' ATCCCTAAGTCCGATCATGCTAACATT 3' (Wait, no! I think the confusion is between coding and template strands. The original DNA is the coding strand (5'→3'), so the complementary DNA strand (template strand) is 3'→5' as A T C C C T A A G T C C G A T C A T G C T A A C A T T, so when writing the complementary DNA strand (the other DNA strand) in 5'→3' direction, we reverse it, but actually, the two DNA strands are antiparallel, so the complementary strand is 3'→5' as A T C C C T A A G T C C G A T C A T G C T A A C A T T, so the 5'→3' of the complementary strand is the reverse, but maybe the question just wants the complementary bases in 3'→5' or 5'→3'? Wait, the original DNA is 5'→3', so the complementary DNA strand should be 3'→5' with complementary bases, but the question has a blank with 5' and 3' ends, so we need to write it 5'→3', so reverse the 3'→5' complement.
But let's do it correctly:
Original DNA: 5' T A G G G A T T C A G G C T A G T A C G A T T G T A A 3'
Complementary bases (A-T, C-G): A T C C C T A A G T C C G A T C A T G C T A A C A T T (this is 3'→5' because the original is 5'→3', so they are antiparallel)
To write this complementary strand in 5'→3' direction, we reverse the order: T T A C A A T C G T A C T A G C C T G A A T C C C T A (5'→3')
Then mRNA: transcribed from the template DNA (which is the complementary strand, 3'→5'), so mRNA is 5'→3' with U instead of T. So template DNA (3'→5'): A T C C C T A A G T C C G A T C A T G C T A A C A T T
mRNA: U A G G G A U U C A G G C U A G U A C G A U U G U A A (5'→3') → 5' UAGGGATTCAGGCTAGTACGATTGTAA 3'
So the complementary DNA strand (5'→3') is 5' TTACAATCGTACTAGCCTGAATCCCTA 3' (or with correct spacing: 5' TTACAATCGTACTAGCCTGAATCCCTA 3') and mRNA is 5' UAGGGATTCAGG