11-17-20 Transcription & Translation Practice.docx - Name Date Per ... - Free Printable

Let’s solve this step by step.

We are given DNA sequences and asked to find:
- mRNA (messenger RNA) — made from DNA template strand, using base pairing rules (A→U, T→A, C→G, G→C)
- tRNA (transfer RNA) — complementary to mRNA, so it matches the original DNA coding strand (but with U instead of T)
- Amino Acid — use the codon chart (each 3-letter mRNA codon corresponds to one amino acid)

Important note: The DNA shown is likely the coding strand (same as mRNA but with T instead of U), unless specified otherwise. But in transcription, mRNA is built from the template strand, which is complementary to the coding strand.

However, looking at Example 1:

DNA: TAC → mRNA: AUG → tRNA: UAC → Amino Acid: Methionine

That tells us:
- DNA “TAC” is the template strand (because mRNA is complementary: A-U, T-A, C-G → so TAC → AUG)
- Then tRNA is complementary to mRNA: AUG → UAC
- And AUG codes for Methionine (start codon)

So yes — the DNA given is the template strand.

Rule recap:
- DNA template → mRNA: A↔U, T↔A, C↔G, G↔C
- mRNA → tRNA: same rule (complementary bases)
- mRNA codon → look up amino acid on chart

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Now let’s do each example.

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Example 2:

DNA: TTC CAT TAG ATG CCC AGG

Step 1: mRNA (complement of DNA template)

T → A
T → A
C → G
→ First codon: AAC

C → G
A → U
T → A
→ Second codon: GUA

T → A
A → U
G → C
→ Third codon: AUC

A → U
T → A
G → C
→ Fourth codon: UAC

C → G
C → G
C → G
→ Fifth codon: GGG

A → U
G → C
G → C
→ Sixth codon: UCC

Wait — let me write it clearly:

DNA: TTC CAT TAG ATG CCC AGG
mRNA: AAG GUA AUC UAC GGG UCC

Check:

TTC → AAG?
T→A, T→A, C→G → AAG ✔️
CAT → GUA?
C→G, A→U, T→A → GUA ✔️
TAG → AUC?
T→A, A→U, G→C → AUC ✔️
ATG → UAC?
A→U, T→A, G→C → UAC ✔️
CCC → GGG?
C→G, C→G, C→G → GGG ✔️
AGG → UCC?
A→U, G→C, G→C → UCC ✔️

Good.

Step 2: tRNA (complement of mRNA)

mRNA: AAG → tRNA: UUC
mRNA: GUA → tRNA: CAU
mRNA: AUC → tRNA: UAG
mRNA: UAC → tRNA: AUG
mRNA: GGG → tRNA: CCC
mRNA: UCC → tRNA: AGG

Step 3: Amino acids (use mRNA codons)

Look up each mRNA codon in standard genetic code:

AAG → Lysine
GUA → Valine
AUC → Isoleucine
UAC → Tyrosine
GGG → Glycine
UCC → Serine

(You can verify with any codon table — these are standard.)

So Example 2:

mRNA: AAG GUA AUC UAC GGG UCC
tRNA: UUC CAU UAG AUG CCC AGG
AA: Lys Val Ile Tyr Gly Ser

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Example 3:

DNA: CAT GGT ATA CTA GCC ATT

Step 1: mRNA (complement of DNA)

CAT → GUA
GGT → CCA
ATA → UAU
CTA → GAU
GCC → CGG
ATT → UAA

Check:

C→G, A→U, T→A → GUA ✔️
G→C, G→C, T→A → CCA ✔️
A→U, T→A, A→U → UAU ✔️
C→G, T→A, A→U → GAU ✔️
G→C, C→G, C→G → CGG ✔️
A→U, T→A, T→A → UAA ✔️

mRNA: GUA CCA UAU GAU CGG UAA

Step 2: tRNA (complement of mRNA)

GUA → CAU
CCA → GGU
UAU → AUA
GAU → CUA
CGG → GCC
UAA → AUU

Step 3: Amino acids

GUA → Valine
CCA → Proline
UAU → Tyrosine
GAU → Aspartic acid
CGG → Arginine
UAA → STOP (stop codon — no amino acid)

Note: UAA is a stop codon — translation ends here. So we don’t assign an amino acid to it. In many worksheets, they still list “Stop” or leave blank. Looking at Example 1, they included all 6 even though last was stop? Wait — Example 1 had 6 codons and listed 6 amino acids including “Stop”.

In Example 1:

DNA: TAC GCA CCT ACT AGG TGG
mRNA: AUG CGU GGA UGA UCC ACC
tRNA: UAC GCA CCU ACU AGG UGG
AA: Met Arg Gly Stop Ser Thr

They wrote “Stop” for UGA.

So we’ll do same: for UAA, write “Stop”

Thus:

Amino acids: Val, Pro, Tyr, Asp, Arg, Stop

But wait — let’s check if UAA is indeed stop — yes, standard stop codons: UAA, UAG, UGA.

So:

Example 3:

mRNA: GUA CCA UAU GAU CGG UAA
tRNA: CAU GGU AUA CUA GCC AUU
AA: Val Pro Tyr Asp Arg Stop

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Final Answers:

Example 2:
mRNA: AAG GUA AUC UAC GGG UCC
tRNA: UUC CAU UAG AUG CCC AGG
Amino Acids: Lysine, Valine, Isoleucine, Tyrosine, Glycine, Serine

Example 3:
mRNA: GUA CCA UAU GAU CGG UAA
tRNA: CAU GGU AUA CUA GCC AUU
Amino Acids: Valine, Proline, Tyrosine, Aspartic acid, Arginine, Stop

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Final Answer:

Example 2:
mRNA: AAG GUA AUC UAC GGG UCC
tRNA: UUC CAU UAG AUG CCC AGG
Amino Acids: Lysine, Valine, Isoleucine, Tyrosine, Glycine, Serine

Example 3:
mRNA: GUA CCA UAU GAU CGG UAA
tRNA: CAU GGU AUA CUA GCC AUU
Amino Acids: Valine, Proline, Tyrosine, Aspartic acid, Arginine, Stop