DNA Transcription and Translation Activity (Middle School and Up) - Free Printable

Let’s solve this step by step.

We are given DNA sequences for three organisms. We need to:

1. Transcribe DNA → mRNA (remember: A→U, T→A, C→G, G→C)
2. Translate mRNA → tRNA codons (tRNA is complementary to mRNA — so A↔U, C↔G)
3. Use the genetic code to find which amino acid each mRNA codon codes for.

Note: The worksheet says “tRNA Codons” — but technically, tRNA has anticodons that pair with mRNA codons. So we’ll write the tRNA anticodon that matches the mRNA codon.

Also note: In transcription, DNA template strand is used to make mRNA. But here, the DNA shown looks like the coding strand (same as mRNA except T→U). Wait — let’s check Organism 1:

DNA: AAA → if this is the template strand, mRNA would be UUU.
But in standard worksheets, when they list “DNA” and ask for mRNA transcription, they usually mean the template strand unless specified otherwise.

Wait — look at Organism 1: DNA = AAA, UCG, ATG, TGG

If DNA is template strand:
- AAA → mRNA = UUU
- UCG → wait, DNA doesn’t have U! That’s a problem.

Ah — here’s the key: The DNA listed must be the coding strand, because it contains “UCG” — which has Uracil? No — DNA should not have U. This is likely a typo or mislabeling.

Actually — looking again: Organism 1 DNA: AAA, UCG, ATG, TGG — “UCG” has a ‘U’? That can’t be right for DNA.

Wait — perhaps it’s a mistake in the worksheet? Or maybe it’s meant to be RNA? But the title says “DNA Transcription”.

Let me re-read: The column says “DNA:” and lists AAA, UCG, ATG, TGG.

But DNA uses A, T, C, G — NOT U. So “UCG” must be a typo — probably meant “TCG”.

Similarly, in Organism 2: CAC, AAA, ACA, ATG, ATA, TTA, GTA, TTC, TCC — all valid DNA bases.

Organism 3: ATA, TTA, AAA, ATG, TTC, ACA, TCC, GTA — also valid.

So likely, in Organism 1, “UCG” is a typo and should be “TCG”.

I will assume that “UCG” in Organism 1 is meant to be “TCG” — since DNA cannot have U.

So corrected Organism 1 DNA: AAA, TCG, ATG, TGG

Now proceed.

Step 1: Transcribe DNA → mRNA

Rule: For transcription, if DNA is the template strand, then:
DNA base → mRNA base
A → U
T → A
C → G
G → C

But if the DNA given is the coding strand (non-template), then mRNA is same as coding strand except T→U.

In most school worksheets, when they say “DNA” and list sequences like this, and ask for mRNA transcription, they intend for you to treat the DNA as the template strand.

BUT — let’s test with known start codon.

ATG in DNA (template) → mRNA = UAC? No — ATG template → mRNA = UAC? Wait no:

Template DNA: A → mRNA U
T → A
G → C
So ATG (template) → mRNA = UAC? But UAC is tyrosine, not methionine.

Methionine is coded by AUG in mRNA.

So if DNA template is TAC → mRNA = AUG.

Therefore, if the DNA sequence given includes “ATG”, and if that’s the template strand, mRNA would be UAC — which is wrong for start.

Alternatively, if the DNA given is the coding strand, then ATG in DNA → mRNA = AUG — which is correct for methionine/start.

That makes more sense.

Also, in many textbooks, when they show “DNA sequence” and say “transcribe to mRNA”, they often mean the coding strand, so you just replace T with U.

Let me verify with common practice.

Example: If DNA coding strand is ATG, mRNA is AUG.

Yes — that’s standard in intro bio.

Moreover, in the worksheet, for Organism 1, DNA has “ATG” — which if coding strand, mRNA = AUG → methionine.

And “AAA” → mRNA = AAA → lysine.

“TCG” → mRNA = UCG → serine.

“TGG” → mRNA = UGG → tryptophan.

That works.

Whereas if template, ATG → UAC (tyrosine), which is less common as a starting point.

So I think the DNA listed is the coding strand.

Therefore, to get mRNA: replace T with U.

Then, tRNA anticodon is complementary to mRNA codon.

Then, use genetic code to find amino acid from mRNA codon.

Let’s do Organism 1 first.

Organism 1:

DNA (coding): AAA, TCG, ATG, TGG

mRNA: replace T with U → AAA, UCG, AUG, UGG

tRNA anticodons: complementary to mRNA

mRNA AAA → tRNA UUU
mRNA UCG → tRNA AGC
mRNA AUG → tRNA UAC
mRNA UGG → tRNA ACC

Amino acids (from mRNA codons):

AAA → Lysine
UCG → Serine
AUG → Methionine
UGG → Tryptophan

Now Organism 2:

DNA: CAC, AAA, ACA, ATG, ATA, TTA, GTA, TTC, TCC

mRNA: replace T with U → CAC, AAA, ACA, AUG, AUA, UUA, GUA, UUC, UCC

tRNA anticodons:

CAC → GUG
AAA → UUU
ACA → UGU
AUG → UAC
AUA → UAU
UUA → AAU
GUA → CAU
UUC → AAG
UCC → AGG

Amino acids:

CAC → Histidine
AAA → Lysine
ACA → Threonine
AUG → Methionine
AUA → Isoleucine
UUA → Leucine
GUA → Valine
UUC → Phenylalanine
UCC → Serine

Organism 3:

DNA: ATA, TTA, AAA, ATG, TTC, ACA, TCC, GTA

mRNA: AUA, UUA, AAA, AUG, UUC, ACA, UCC, GUA

tRNA anticodons:

AUA → UAU
UUA → AAU
AAA → UUU
AUG → UAC
UUC → AAG
ACA → UGU
UCC → AGG
GUA → CAU

Amino acids:

AUA → Isoleucine
UUA → Leucine
AAA → Lysine
AUG → Methionine
UUC → Phenylalanine
ACA → Threonine
UCC → Serine
GUA → Valine

Now, let’s write the answers clearly.

Final Answer:

Organism 1:
mRNA: AAA, UCG, AUG, UGG
tRNA Codons: UUU, AGC, UAC, ACC
Amino Acids: Lysine, Serine, Methionine, Tryptophan

Organism 2:
mRNA: CAC, AAA, ACA, AUG, AUA, UUA, GUA, UUC, UCC
tRNA Codons: GUG, UUU, UGU, UAC, UAU, AAU, CAU, AAG, AGG
Amino Acids: Histidine, Lysine, Threonine, Methionine, Isoleucine, Leucine, Valine, Phenylalanine, Serine

Organism 3:
mRNA: AUA, UUA, AAA, AUG, UUC, ACA, UCC, GUA
tRNA Codons: UAU, AAU, UUU, UAC, AAG, UGU, AGG, CAU
Amino Acids: Isoleucine, Leucine, Lysine, Methionine, Phenylalanine, Threonine, Serine, Valine