Transcription Worksheet | PDF - Free Printable

Let’s work through each part of the worksheet step by step.

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Part 1: Fill in missing DNA or mRNA sequences

We know that during transcription, DNA is used to make mRNA. The base pairing rules are:

- In DNA → A pairs with T, C pairs with G
- In RNA (mRNA) → A pairs with U (instead of T), C pairs with G

So when going from DNA to mRNA:
- DNA’s A → mRNA’s U
- DNA’s T → mRNA’s A
- DNA’s C → mRNA’s G
- DNA’s G → mRNA’s C

When going from mRNA to DNA, we reverse it:
- mRNA’s A → DNA’s T
- mRNA’s U → DNA’s A
- mRNA’s C → DNA’s G
- mRNA’s G → DNA’s C

Also note: The DNA strand that is transcribed is called the *antisense* strand — and it’s complementary to the mRNA. So if you’re given mRNA, you can find the antisense DNA by replacing U→A, A→T, C→G, G→C.

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Question 1:

Given mRNA:
`AUG ACU AGC UGG GGG UAU UAC UUU UAG`

We need to find the DNA sequence (the antisense strand).

Replace each mRNA base with its DNA complement:

- A → T
- U → A
- G → C
- C → G

So:

mRNA: A U G A C U A G C U G G G G G U A U U A C U U U U A G
DNA: T A C T G A T C G A C C C C C A T A A T G A A A A T C

Wait — let’s do this carefully group by group:

AUG → TAC
ACU → TGA
AGC → TCG
UGG → ACC
GGG → CCC
UAU → ATA
UAC → ATG
UUU → AAA
UAG → ATC

So DNA = `TAC TGA TCG ACC CCC ATA ATG AAA ATC`

But wait — looking at question 2, they give a DNA sequence starting with “TAC CGC...” which matches the first triplet here as “TAC”. That suggests maybe the DNA given in Q2 is the template? Let’s hold on.

Actually, for Question 1, since only mRNA is given, we fill in the DNA (antisense strand) as above.

Final answer for Q1 DNA:
TAC TGA TCG ACC CCC ATA ATG AAA ATC

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Question 2:

Given DNA:
`TAC CGC TCC GCC GTC GAC AAT ACC ACT`

This is likely the antisense (template) strand, so we transcribe it to mRNA.

Use base pairing:

DNA: T → mRNA: A
DNA: A → mRNA: U
DNA: C → mRNA: G
DNA: G → mRNA: C

Break into triplets:

TAC → AUG
CGC → GCG
TCC → AGG
GCC → CGG
GTC → CAG
GAC → CUG
AAT → UUA
ACC → UGG
ACT → UGA

So mRNA = `AUG GCG AGG CGG CAG CUG UUA UGG UGA`

Check: Yes, starts with AUG (start codon), ends with UGA (stop codon). Makes sense.

Final answer for Q2 mRNA:
AUG GCG AGG CGG CAG CUG UUA UGG UGA

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Question 3:

Given DNA:
`ATG CAC CCC CGA AAG GCT GGG AAA AGC`

Again, assuming this is the antisense strand (since it's labeled "DNA" and we're to write mRNA), we transcribe it.

Base pairing:

ATG → UAC
CAC → GUG
CCC → GGG
CGA → GCU
AAG → UUC
GCT → CGA
GGG → CCC
AAA → UUU
AGC → UCG

Wait — but hold on! If this DNA starts with ATG, and we transcribe it directly, we get UAC... but usually the coding strand has ATG (which becomes AUG in mRNA). This might be the *coding* strand? But the worksheet says “fill in either DNA or mRNA”, and doesn’t specify which strand.

Looking back at the instructions: “For each of the following sequences, fill in either the DNA and the mRNA sequence that have been left blank.”

In Q1, mRNA was given → we found DNA (antisense).
In Q2, DNA was given → we found mRNA (assuming DNA is antisense).
In Q3, DNA is given → should we assume same as Q2? i.e., DNA is antisense?

But in Q3, DNA starts with ATG — if that’s antisense, then mRNA would start with UAC — which is not typical. Usually, mRNA starts with AUG.

Alternatively, perhaps in Q3, the DNA given is the *coding* strand (same as mRNA except T instead of U)? But the worksheet doesn't specify.

Wait — look at Part 2 of the worksheet: It shows two DNA strands and an mRNA, and asks to find antisense strand. There, mRNA is `AUC CAC CCC CGA AAG GCU GGG AAA AGC`, and DNA Strand 1 is `ATG CAC CCC CGA AAG GCT GGG AAA AGC` — which is almost identical to mRNA but with T instead of U.

That means: DNA Strand 1 is the *coding* strand (non-template), and DNA Strand 2 is the antisense (template) strand.

And mRNA is complementary to antisense strand, so same as coding strand (with U instead of T).

So in Q3, if DNA is given as `ATG CAC CCC CGA AAG GCT GGG AAA AGC`, and if we assume it’s the coding strand (like in Part 2), then mRNA would be the same but with U instead of T:

ATG → AUG
CAC → CAC
CCC → CCC
CGA → CGA
AAG → AAG
GCT → GCU
GGG → GGG
AAA → AAA
AGC → AGC

So mRNA = `AUG CAC CCC CGA AAG GCU GGG AAA AGC`

But wait — in Part 2, they show exactly this! And they label DNA Strand 1 as having that sequence, and mRNA as matching it with U instead of T.

Therefore, for consistency, in Q3, since DNA is given and looks like the coding strand (starts with ATG, matches mRNA pattern), we should convert T to U to get mRNA.

Thus, mRNA for Q3:
AUG CAC CCC CGA AAG GCU GGG AAA AGC

But let’s double-check with base pairing if we treat DNA as antisense:

If DNA = ATG CAC ... and it’s antisense, then mRNA = UAC GUG ... — which does NOT match Part 2.

Since Part 2 uses the same sequence and treats DNA Strand 1 as coding (so mRNA = same with U), we’ll go with that.

So final answer for Q3 mRNA:
AUG CAC CCC CGA AAG GCU GGG AAA AGC

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Part 2: Find antisense strands

They give:

DNA Strand 1: `ATG CAC CCC CGA AAG GCT GGG AAA AGC`
DNA Strand 2: `TAG GTG GGG GCT TTC CGA CCC TTT TCG`
mRNA: `AUC CAC CCC CGA AAG GCU GGG AAA AGC`

We are to find which DNA strand is the antisense (template) strand.

Antisense strand is complementary to mRNA.

Compare mRNA to DNA strands.

mRNA: AUC CAC CCC CGA AAG GCU GGG AAA AGC

Check against DNA Strand 1: ATG CAC CCC CGA AAG GCT GGG AAA AGC
→ Almost same, but DNA has T where mRNA has U. So this is the *coding* strand, not antisense.

Check DNA Strand 2: TAG GTG GGG GCT TTC CGA CCC TTT TCG

Now, compare to mRNA:

mRNA: AUC CAC CCC CGA AAG GCU GGG AAA AGC
DNA2: TAG GTG GGG GCT TTC CGA CCC TTT TCG

Are they complementary?

Let’s pair them:

mRNA: A U C C A C C C C C G A A A G G C U G G G A A A A G C
DNA2: T A G G T G G G G G C T T T C C G A C C C T T T T C G

Check base pairing:

A-T? mRNA A vs DNA T → yes
U-A? mRNA U vs DNA A → yes
C-G? mRNA C vs DNA G → yes
C-G? mRNA C vs DNA G → yes
A-T? mRNA A vs DNA T → yes
C-G? mRNA C vs DNA G → yes
... and so on.

Yes! Each base in mRNA pairs with the corresponding base in DNA Strand 2.

So DNA Strand 2 is the antisense strand.

Answer for Part 2: DNA Strand 2

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Part 3: What are the steps of transcription?

Transcription is making RNA from DNA. Three main steps:

1. Initiation: RNA polymerase binds to the promoter region on DNA and unwinds the double helix.
2. Elongation: RNA polymerase reads the antisense (template) strand and builds mRNA by adding complementary nucleotides (A-U, C-G).
3. Termination: When RNA polymerase reaches a stop signal (terminator), it releases the mRNA strand and detaches from DNA.

Simple version:

- Step 1: Start – enzyme attaches to DNA.
- Step 2: Build – enzyme makes RNA copy.
- Step 3: Stop – enzyme lets go, RNA is done.

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Final Answers:

→ For Q1 DNA: TAC TGA TCG ACC CCC ATA ATG AAA ATC
→ For Q2 mRNA: AUG GCG AGG CGG CAG CUG UUA UGG UGA
→ For Q3 mRNA: AUG CAC CCC CGA AAG GCU GGG AAA AGC
→ For Part 2: DNA Strand 2 is the antisense strand
→ For Part 3: Initiation, Elongation, Termination

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Final Answer:
1. DNA: TAC TGA TCG ACC CCC ATA ATG AAA ATC
2. mRNA: AUG GCG AGG CGG CAG CUG UUA UGG UGA
3. mRNA: AUG CAC CCC CGA AAG GCU GGG AAA AGC
Antisense strand: DNA Strand 2
Steps of transcription: Initiation, Elongation, Termination