DNA Mutations lab worksheet with codon chart and questions on genetic changes.

Let’s solve this step by step.

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Question 1: Transcribe DNA → mRNA, then translate to amino acids

We’re given a DNA sequence:

DNA: S I T G A C A T A C T A
(But wait — that doesn’t look right. Looking at the table in the image, it seems like “S”, “I”, “T” are placeholders or maybe mislabeled? Actually, looking again — the table shows:

DNA: S I T G A C A T A C T A
mRNA: G U A C U G U A U G A U
Amino Acid: Val Leu Val Met Asp

Wait — that can’t be right because DNA should have A, T, C, G — not S, I, T. Let me re-read.

Actually, looking closely at the table in the image (even though we don’t describe images), the user probably meant:

The DNA sequence is: G T A C T G T A T G A T

Because under “DNA” row it says: G T A C T G T A T G A T
Then mRNA is transcribed as: C A U G A C A U A C U A
Wait — no, let’s do it properly.

Hold on — transcription means replacing each DNA base with its RNA complement:

- DNA A → RNA U
- DNA T → RNA A
- DNA C → RNA G
- DNA G → RNA C

So if DNA is: G T A C T G T A T G A T

Then mRNA is:

G → C
T → A
A → U
C → G
T → A
G → C
T → A
A → U
T → A
G → C
A → U
T → A

So mRNA = C A U G A C A U A C U A

Now group into codons (groups of 3):

CAU | GAC | AUA | CUA

Now use genetic code:

- CAU → Histidine (His)
- GAC → Aspartic acid (Asp)
- AUA → Isoleucine (Ile)
- CUA → Leucine (Leu)

But the table in the problem says:

mRNA: G U A C U G U A U G A U
Amino Acid: Val Leu Val Met Asp

That suggests the DNA was actually: C A T G A C A T A C T A

Let’s check:

DNA: C A T G A C A T A C T A
Transcribe to mRNA:

C → G
A → U
T → A
G → C
A → U
C → G
A → U
T → A
A → U
C → G
T → A
A → U

mRNA: G U A C U G U A U G A U

Group: GUA | CUG | UAU | GAU

Codon table:

- GUA → Valine (Val)
- CUG → Leucine (Leu)
- UAU → Tyrosine (Tyr) ← but table says “Val”? Wait, no — table says third amino acid is “Val”? That doesn’t match.

Wait — table says:

mRNA: G U A C U G U A U G A U
Amino Acid: Val Leu Val Met Asp

That would mean:

GUA → Val ✔
CUG → Leu ✔
UAU → Tyr ✘ but they say “Val” — that’s wrong.
GAU → Asp ✔
And there’s an extra “Met” — which comes from AUG.

Ah! Maybe the mRNA is grouped differently? Or perhaps the DNA is different.

Looking back — maybe the DNA sequence is: C A T G A C A T A C T A — but when transcribed, mRNA is G U A C U G U A U G A U — and if we read it as:

GUA → Val
CUG → Leu
UAU → Tyr — but they wrote “Val” — that must be a typo? Or maybe I’m misreading.

Wait — the table in the problem has:

DNA: S I T G A C A T A C T A — that’s weird. Probably “S I T” is a mistake — maybe it’s supposed to be “C A T”?

Alternatively, perhaps the DNA is: C A T G A C A T A C T A

mRNA: G U A C U G U A U G A U

Now, if we split as: GUA CUG UAU GAU → Val, Leu, Tyr, Asp

But the table says: Val, Leu, Val, Met, Asp — that’s 5 amino acids, but we only have 4 codons.

Unless... maybe the DNA is longer? Or perhaps the “S I T” is meant to be ignored? This is confusing.

Wait — let’s look at Question 2 for clues.

In Question 2:

Sequence 1: GTT CGA GTA CTA
Sequence 2: GTT GAA GTA CTA

It says: “What is the difference between the two? The second codon is GAA. If originally was GCA.”

Wait — original Sequence 1 has “CGA”, Sequence 2 has “GAA”.

So mutation changed CGA → GAA.

CGA codes for Arginine (Arg)
GAA codes for Glutamic acid (Glu)

So substitution mutation — one base changed: C → G in first position of codon.

Result: arginine → glutamic acid.

Back to Question 1 — perhaps the DNA sequence is meant to be: C A T G A C A T A C T A

mRNA: G U A C U G U A U G A U

But to get “Met”, we need AUG — which would come from DNA “TAC”

In our mRNA: positions 7-9: U A U → Tyr
positions 10-12: G A U → Asp

No AUG.

Unless the DNA is: C A T G A C A T A C T A — but if we shift reading frame? No, that’s not standard.

Perhaps the table has a typo, and “Val” should be “Tyr”, and “Met” shouldn’t be there.

But let’s assume the intended DNA is: C A T G A C A T A C T A

mRNA: G U A C U G U A U G A U

Codons: GUA (Val), CUG (Leu), UAU (Tyr), GAU (Asp)

But the table says: Val, Leu, Val, Met, Asp — which doesn't match.

Another possibility: maybe the DNA is C A T G A C A T A C T A, but when transcribed, it's G U A C U G U A U G A U, and they grouped it as:

GUA CUG UAU GAU — still 4 codons.

Unless the last "A" is part of next, but no.

Perhaps the DNA is 15 bases? Let's count the letters in the table:

DNA: S I T G A C A T A C T A — that's 12 characters.

If we ignore S,I,T and take G A C A T A C T A — that's 9, not enough.

This is messy. Let's try a different approach.

Look at the mRNA given in the table: G U A C U G U A U G A U

That's 12 bases.

Grouped as: GUA CUG UAU GAU — 4 codons.

Amino acids should be: Val, Leu, Tyr, Asp

But the table says: Val, Leu, Val, Met, Asp — which is 5 items. That doesn't add up.

Unless "Val" is repeated by mistake, and "Met" is for AUG, which isn't there.

Perhaps the mRNA is GUA CUG UAU GAU, and they meant to write Tyr instead of Val, and omit Met.

But let's move to Question 2, which is clearer.

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Question 2:

Sequence 1: GTT CGA GTA CTA
Sequence 2: GTT GAA GTA CTA

Difference: second codon changed from CGA to GAA.

Original codon: CGA → codes for Arginine (Arg)
Mutated codon: GAA → codes for Glutamic acid (Glu)

Type of mutation: substitution (one base changed: C to G in first position)

Effect: amino acid changed from arginine to glutamic acid.

The question says: "if originally was GCA" — but in Sequence 1 it's CGA, not GCA.

GCA also codes for Alanine (Ala), but here it's CGA.

Probably a typo in the question — it should be "originally was CGA".

So answer: substitution mutation; arginine replaced by glutamic acid.

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Question 3: Analyze these two DNA sequences — but they're not provided in the text you gave. In the image, it might be cut off. Since you didn't provide them, I'll skip for now.

But for Question 1, let's assume the DNA is: C A T G A C A T A C T A

mRNA: G U A C U G U A U G A U

Amino acids: Val (GUA), Leu (CUG), Tyr (UAU), Asp (GAU)

But the table says Val, Leu, Val, Met, Asp — which is incorrect.

Perhaps the DNA is: C A T G A C A T A C T A but they want us to use a different reading frame? Unlikely.

Another idea: maybe "S I T" is "CAT" misspelled? S looks like C, I like A, T like T — so CAT.

Then DNA: CAT GAC ATA CTA

mRNA: GUA CUG UAU GAU

Same as before.

Perhaps the last "A" is extra, or something.

Let's calculate based on standard rules.

For Question 1, I think the intended answer is:

DNA: CAT GAC ATA CTA
mRNA: GUA CUG UAU GAU
Amino acids: Val, Leu, Tyr, Asp

But since the table says otherwise, and to match their format, perhaps they have a different sequence.

Notice that in the mRNA they have "G U A C U G U A U G A U" — if we group as GUA CUG UAU GAU, but they list 5 amino acids, so maybe it's GUA CUG UAU GAU — and "Val" is listed twice by mistake, and "Met" is for AUG which isn't there.

Perhaps the DNA is: C A T G A C A T A C T A but when transcribed, it's G U A C U G U A U G A U, and if we consider that "UAU" is sometimes misread, but no.

Let's look for AUG in the mRNA: positions 8-10: U G A — that's stop codon, not Met.

Positions 9-11: G A U — Asp.

No AUG.

Unless the DNA has "TAC" which gives "AUG" in mRNA.

In our DNA: position 7-9: A T A — mRNA U A U

Position 10-12: C T A — mRNA G A U

No TAC.

Perhaps the DNA is: C A T G A C T A C T A — but that's 11 bases.

I think there's a mistake in the problem or my interpretation.

To resolve, let's assume that for Question 1, the DNA sequence is meant to be transcribed as per standard rules, and we'll go with:

DNA: CAT GAC ATA CTA
mRNA: GUA CUG UAU GAU
Amino acids: Val, Leu, Tyr, Asp

But since the table in the problem shows different, and to align with what they might expect, perhaps they have:

Another possibility: maybe "S I T" is "GTA" or something.

Let's give up and do Question 2 first.

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Question 2 Answer:

The difference is that in Sequence 1, the second codon is CGA, which codes for arginine (Arg). In Sequence 2, it's GAA, which codes for glutamic acid (Glu).

This is a substitution mutation (one nucleotide changed: C to G in the first position of the codon).

The effect is that the amino acid changes from arginine to glutamic acid.

The question says "if originally was GCA" — but GCA codes for alanine, while here it's CGA for arginine. Probably a typo, and it should be "originally was CGA".

So final answer for Q2: substitution mutation; arginine is replaced by glutamic acid.

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For Question 1, let's force-fit to their table.

Their table has:

DNA: S I T G A C A T A C T A — let's assume S= C, I=A, T=T, so CAT GAC ATA CTA

mRNA: G U A C U G U A U G A U

Now, if we group as: GUA CUG UAU GAU — but they have 5 amino acids listed: Val, Leu, Val, Met, Asp

Perhaps they grouped it as GUA CUG UAU GAU, but wrote "Val" for UAU by mistake, and "Met" for something else.

Maybe the mRNA is read as GUA CUG UAU GAU, and "Val" is for GUA, "Leu" for CUG, then "Val" might be a error for "Tyr", and "Met" might be for AUG which isn't there, and "Asp" for GAU.

Perhaps the DNA is longer. Let's count the bases in DNA row: S,I,T,G,A,C,A,T,A,C,T,A — 12 bases.

mRNA: 12 bases.

5 amino acids would require 15 bases, so impossible.

Unless they include start/stop, but no.

I think the best is to correct it.

Perhaps "S I T" is not part of the sequence, and DNA starts from G: G A C A T A C T A — 9 bases.

mRNA: C U G U A U G A U

Codons: CUG UAU GAU — Leu, Tyr, Asp

Not matching.

Another idea: perhaps the DNA is: C A T G A C A T A C T A and they want us to transcribe and translate, and the table is for reference, but we need to fill it.

In the table, under DNA, it's written as "S I T G A C A T A C T A", but likely "S I T" is "CAT" , so DNA: CAT GAC ATA CTA

mRNA: GUA CUG UAU GAU

Amino acids: Val, Leu, Tyr, Asp

But the table has "Val Leu Val Met Asp" — so perhaps for educational purposes, they have a different sequence.

Let's look at the mRNA they have: G U A C U G U A U G A U

If we group as GUA CUG UAU GAU, but if we shift: UAC UGU AUG AU — not good.

Perhaps it's GUA CUG UAU GAU, and "Val" is listed twice, and "Met" is a mistake.

I recall that in some contexts, "Met" is for start, but here no AUG.

Let's calculate the amino acids for mRNA GUA CUG UAU GAU:

- GUA: Val
- CUG: Leu
- UAU: Tyr
- GAU: Asp

So for Question 1, the answer should be:

mRNA: GUA CUG UAU GAU
Amino acids: Val, Leu, Tyr, Asp

But since the problem's table says otherwise, and to match their expected answer, perhaps they have a different intention.

Notice that in the mRNA, if we have "U A U G" — that could be UAU and G, but not.

Another thought: perhaps the DNA is: C A T G A C A T A C T A but when transcribed, it's G U A C U G U A U G A U, and they consider the codons as GUA, CUG, UAU, GAU, but in the amino acid row, they have "Val Leu Val Met Asp" — which might be a typo, and "Val" should be "Tyr", and "Met" should not be there, or perhaps "Met" is for the start, but it's not.

Perhaps the first codon is for start, but GUA is not start.

I think for the sake of completing, I'll go with the correct biology.

So for Question 1:

DNA: CAT GAC ATA CTA
mRNA: GUA CUG UAU GAU
Amino acids: Valine, Leucine, Tyrosine, Aspartic acid

But to match the format, perhaps write as Val, Leu, Tyr, Asp

For Question 2:

Mutation type: substitution
Change: CGA (Arg) to GAA (Glu)
Effect: arginine replaced by glutamic acid

For Question 3, since not provided, skip.

But in the user's message, Question 3 is "Now analyze these two DNA sequences" but no sequences given, so perhaps in the image it's there, but since we can't see, we'll omit.

So final answers:

Question 1:
mRNA: GUA CUG UAU GAU
Amino acids: Val, Leu, Tyr, Asp

Question 2:
The difference is that the second codon changed from CGA to GAA. This is a substitution mutation. Originally, CGA coded for arginine (Arg), and after mutation, GAA codes for glutamic acid (Glu). So the amino acid changed from arginine to glutamic acid.

Question 3: Not provided.

But to box the answer as per instruction.

Since the user might expect the table filled as per their format, and to avoid confusion, let's assume that for Question 1, the DNA is CAT GAC ATA CTA, and we transcribe and translate correctly.

Perhaps "S I T" is "GTA" — S=G, I=T, T=A? Then DNA: GTA GAC ATA CTA

mRNA: CAU CUG UAU GAU

Amino acids: His, Leu, Tyr, Asp — not matching.

Or S=C, I=A, T=G — CAG GAC ATA CTA

mRNA: GUC CUG UAU GAU — Val, Leu, Tyr, Asp — same as before.

I think it's consistent.

So I'll go with that.

Final Answer for Question 1:
mRNA: GUA CUG UAU GAU
Amino acids: Val, Leu, Tyr, Asp

For Question 2:
Substitution mutation; arginine is replaced by glutamic acid.

Now for the boxed answer, since there are multiple parts, perhaps list them.

But the instruction is to provide final answer after reasoning.

So:

Final Answer:
For Question 1:
- mRNA sequence: GUA CUG UAU GAU
- Amino acid sequence: Val, Leu, Tyr, Asp

For Question 2:
- Type of mutation: substitution
- Change: CGA (arginine) to GAA (glutamic acid)
- Effect: arginine is replaced by glutamic acid

For Question 3: Sequences not provided, so cannot analyze.

But to make it neat.

Perhaps the user expects only the answers as per the worksheet.

Another idea: in Question 1, the DNA is given as "S I T G A C A T A C T A", and if we take S= C, I= A, T= T, then CAT GAC ATA CTA, and mRNA GUA CUG UAU GAU, and amino acids Val, Leu, Tyr, Asp.

And in the table, they have "Val Leu Val Met Asp" which is likely a mistake, so we correct it.

So I'll proceed.

Final Answer:

For Question 1:
mRNA: GUA CUG UAU GAU
Amino acids: Val, Leu, Tyr, Asp

For Question 2:
The mutation is a substitution. The codon changed from CGA (which codes for arginine) to GAA (which codes for glutamic acid), so the amino acid changed from arginine to glutamic acid.

For Question 3:
[Sequences not provided in query]