Protein Synthesis Worksheet showing steps of transcription and translation with DNA, mRNA, tRNA, and amino acids.

Let's go through the Protein Synthesis Worksheet step by step and explain each part. The goal is to understand how DNA is transcribed into mRNA, which is then translated into a sequence of amino acids using tRNA and the genetic code.

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🔬 Overview of the Process

1. DNA → mRNA (Transcription)
- DNA base pairing: A ↔ T, G ↔ C
- In transcription, RNA uses U instead of T

2. mRNA → Protein (Translation)
- mRNA codons (3-base sequences) are read by tRNA with complementary anti-codons
- Each codon codes for a specific amino acid (using the Codon Table)

---

## ✔ Problem 1–4 (First Sequence)

Given:
```
DNA: A T G G T A G C T A A C C T T
T A C C A T C G A T T G G A A
```

Step 1: Complementary DNA strand (already filled in)

- Original DNA: `A T G G T A G C T A A C C T T`
- Complement: `T A C C A T C G A T T G G A A` ✔
✔️ Correct — A↔T, G↔C

---

Step 2: Transcribe to mRNA

- mRNA is made from the template strand (bottom DNA strand), so we use it to make mRNA.
- Replace T with U in RNA.

Template DNA: `T A C C A T C G A T T G G A A`
→ mRNA: `A U G G U A G C U A A C C U U` ✔

✔️ Correct transcription

---

Step 3: tRNA anti-codons

tRNA brings amino acids based on anti-codons that pair with mRNA codons.

mRNA: `A U G G U A G C U A A C C U U`
→ tRNA anti-codons:
- AUG → UAC
- GUA → CUG
- GCU → CGA
- AAC → UUG
- CUU → GAA

So tRNA: `U A C C U G C G A U U G G A A` ✔
(Each tRNA anti-codon matches the mRNA codon via base pairing)

---

Step 4: Amino Acids

Now translate mRNA codons using the Codon Table:

| mRNA Codon | Amino Acid |
|------------|------------|
| AUG | Methionine (Start) |
| GUA | Valine |
| GCU | Alanine |
| AAC | Asparagine |
| CUU | Leucine |

✔ So amino acids: Methionine, Valine, Alanine, Asparagine, Leucine

---

Step 5: Where is mRNA synthesized?

> Answer: Transcription
- mRNA is synthesized during transcription, not translation.
- Translation = protein building; Transcription = DNA → RNA

✔ Answer: transcription

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Step 6: Does mRNA have codons or anti-codons?

> Answer: codons
- mRNA has codons (triplets that code for amino acids).
- tRNA has anti-codons (complementary to mRNA codons).

✔ Answer: codons

---

## ✔ Problem 7–10 (Second Sequence)

Given:
```
DNA: C A G G A A T T G C T C G A T
G T C C T T A A C G A G C T A
```

Step 7: Complementary DNA strand

Original DNA: `C A G G A A T T G C T C G A T`
Complement: `G T C C T T A A C G A G C T A` ✔
✔️ Correct

---

Step 8: mRNA (from template strand)

Template DNA: `G T C C T T A A C G A G C T A`
→ mRNA: `C A G G A A U U G C U C G A U` ✔
(T → U in RNA)

---

Step 9: tRNA anti-codons

mRNA: `C A G G A A U U G C U C G A U`
tRNA anti-codons must be complementary:

| mRNA | Anti-codon (tRNA) |
|------|-------------------|
| CAG | GUC |
| GAA | CUU |
| UUG | AAC |
| CUC | GAG |
| GAU | CUA |

So tRNA: `G U C C U U A A C G A G C U A` ✔

---

Step 10: Amino Acids

Translate mRNA codons:

| mRNA Codon | Amino Acid |
|------------|--------------------|
| CAG | Glutamine |
| GAA | Glutamic Acid |
| UUG | Leucine |
| CUC | Leucine |
| GAU | Aspartic Acid |

But wait — the answer given says:
Valine, Glutamic Acid, Leucine, Leucine, Aspartic Acid

✘ This does not match.

Wait! Let's check the mRNA again.

We said mRNA is: `C A G G A A U U G C U C G A U`
But if we look at the original DNA top strand: `C A G G A A T T G C T C G A T`
Then the template strand is bottom: `G T C C T T A A C G A G C T A`
So mRNA should be: `C A G G A A U U G C U C G A U` → correct.

But now let’s double-check the amino acids:

- CAG → Glutamine (Gln)
- GAA → Glutamic Acid (Glu)
- UUG → Leucine (Leu)
- CUC → Leucine (Leu)
- GAU → Aspartic Acid (Asp)

So amino acids: Glutamine, Glutamic Acid, Leucine, Leucine, Aspartic Acid

But the worksheet says:
Valine, Glutamic Acid, Leucine, Leucine, Aspartic Acid

That implies the first codon is GUU, not CAG.

Wait — maybe there’s a mistake in the mRNA transcription?

Let’s re-express:

Top DNA: `C A G G A A T T G C T C G A T`
Bottom DNA (template): `G T C C T T A A C G A G C T A`
→ mRNA: `C A G G A A U U G C U C G A U` → correct

But CAG is not Valine.

Wait — could the reading frame be wrong?

No. But look at the tRNA anti-codons listed:
`G U C C U U A A C G A G C U A`

Which means:
- First tRNA anti-codon: GUC → pairs with CAG → Glutamine

But the amino acid written is Valine — which is wrong.

So there’s an error in the key.

Wait — unless the top strand is the coding strand?

Let’s clarify:

In standard biology:
- The template strand is used for transcription.
- The coding strand has the same sequence as mRNA (except T vs U).

Here, the top strand is: `C A G G A A T T G C T C G A T`
The bottom strand is: `G T C C T T A A C G A G C T A`

If the bottom strand is the template, then mRNA = `C A G G A A U U G C U C G A U`

But if the top strand is the coding strand, then mRNA would be identical to top strand (with T→U):
`C A G G A A U U G C U C G A U` — same result.

So mRNA is still: `CAG GAA UUG CUC GAU`

Now:
- CAG → Glutamine
- GAA → Glutamic Acid
- UUG → Leucine
- CUC → Leucine
- GAU → Aspartic Acid

So the correct amino acids are:
Glutamine, Glutamic Acid, Leucine, Leucine, Aspartic Acid

But the key says: Valine, Glutamic Acid, Leucine, Leucine, Aspartic Acid

This suggests the first codon was misread.

Wait — Valine corresponds to GUU, GUC, GUA, GUG.

So if the mRNA started with GUC, that would be Valine.

But our mRNA starts with CAG.

So unless the DNA strand orientation is reversed, this doesn’t make sense.

Wait — look at the tRNA anti-codon: `G U C` — which pairs with CAG → Glutamine

So why is the amino acid labeled Valine?

Ah! There's a mistake in the key.

Unless... did they mean the tRNA anti-codon is CUG for GAC?

Wait — let’s reverse engineer:

Suppose the first amino acid is Valine → codon is GUG, GUC, GUU, GUA

So mRNA codon = GUC → tRNA anti-codon = CAG

But in the mRNA, it's written as `C A G G A A U U G C U C G A U`

So first codon is CAG, not GUC

So the only way Valine appears is if the reading frame starts later.

But the mRNA is written as: `C A G G A A U U G C U C G A U`

So codons:
1. CAG → Glutamine
2. GAA → Glutamic Acid
3. UUG → Leucine
4. CUC → Leucine
5. GAU → Aspartic Acid

No Valine here.

But Valine is only possible if codon is GUC, GUG, etc.

So unless the mRNA is written incorrectly, or the DNA strand is mislabeled, the answer must be wrong.

Wait — perhaps the top strand is the template strand?

Let’s try that.

Suppose top strand is template: `C A G G A A T T G C T C G A T`
Then mRNA = `G U C C U U A A C G A G C U A` ← complement, with U instead of T

So mRNA: `G U C C U U A A C G A G C U A`

Now codons:
1. GUC → Valine ✔
2. CUU → Leucine
3. AAC → Asparagine
4. GAG → Glutamic Acid
5. CUU → Leucine

Wait — but the key shows:
- mRNA: `C A G G A A U U G C U C G A U` → which is complement of bottom strand, so bottom is template.

But if bottom strand is template, mRNA is `C A G G A A U U G C U C G A U`

So first codon: CAG → Glutamine

But the tRNA anti-codon shown is `G U C` → pairs with CAG → correct for Glutamine

But the amino acid is labeled Valine — which is incorrect.

So there is a mistake in the answer key.

Unless the tRNA anti-codon is supposed to be CUG for GAC, but that’s not matching.

Wait — perhaps the DNA strands are swapped?

Look back at the worksheet:

It says:
```
DNA: C A G G A A T T G C T C G A T
G T C C T T A A C G A G C T A
```

And below, mRNA: `C A G G A A U U G C U C G A U`

So mRNA matches the complement of the bottom strand → so bottom strand is template

So mRNA = `CAG GAA UUG CUC GAU`

→ Amino acids: Glutamine, Glutamic Acid, Leucine, Leucine, Aspartic Acid

But the key says: Valine, Glutamic Acid, Leucine, Leucine, Aspartic Acid

So Valine is wrong.

Unless the first codon is GUC, which would require mRNA to start with GUC, meaning the template strand is the top one.

But the bottom strand is longer and ends with A, while top ends with T.

Wait — perhaps the top strand is the coding strand, and bottom is template.

Then mRNA = complement of bottom = `C A G G A A U U G C U C G A U`

Same as before.

So no change.

Therefore, the answer key has an error.

The correct amino acid sequence should be:

> Glutamine, Glutamic Acid, Leucine, Leucine, Aspartic Acid

But the key says Valine, which is incorrect.

Unless the mRNA is written backwards?

No — it's clearly `C A G G A A U U G C U C G A U`

So CAG is first.

Thus, Valine is not correct.

---

## ✔ Final Answers (Corrected)

First Sequence (1–4)

1. Complementary DNA: `T A C C A T C G A T T G G A A` ✔
2. mRNA: `A U G G U A G C U A A C C U U` ✔
3. tRNA: `U A C C U G C G A U U G G A A` ✔
4. Amino Acids: Methionine, Valine, Alanine, Asparagine, Leucine ✔
(All correct)

5. mRNA is synthesized in: transcription ✔
6. mRNA has: codons ✔

---

Second Sequence (7–10)

7. Complementary DNA: `G T C C T T A A C G A G C T A` ✔
8. mRNA: `C A G G A A U U G C U C G A U` ✔
9. tRNA: `G U C C U U A A C G A G C U A` ✔
10. Amino Acids: Glutamine, Glutamic Acid, Leucine, Leucine, Aspartic Acid

✘ But the key says: Valine, Glutamic Acid, Leucine, Leucine, Aspartic Acid

✘ Error in Key

Correction:
- The first codon is CAG, which codes for Glutamine, not Valine.
- Valine requires GUC, GUG, GUU, GUA — none of which appear in this sequence.

So the answer key is wrong for this section.

---

## ✔ Summary

| Question | Correct Answer |
|--------|----------------|
| 5 | transcription |
| 6 | codons |
| 10 | Glutamine, Glutamic Acid, Leucine, Leucine, Aspartic Acid |

> ⚠️ Note: The key contains an error in question 10. The first amino acid should be Glutamine, not Valine.

---

## 🧠 Final Explanation

- DNA → mRNA: Transcription (uses base pairing, T→U)
- mRNA → Protein: Translation (codons → amino acids via tRNA)
- tRNA anti-codon pairs with mRNA codon
- Always use the template strand (non-coding strand) for transcription
- Use the Codon Table to find amino acids

✔ Only when you follow these rules will you get accurate results.

Let me know if you'd like a printable version or a corrected key!