Amoeba Sisters Video Recap: Mutations worksheet featuring educational content on genetic mutations, including a DNA illustration and a cartoon depiction of mRNA codons.

Let’s go step by step to solve each question on the worksheet.

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Question 1: What is a mutation?

A mutation is a change in the DNA sequence. Think of DNA like an instruction manual for building and running your body. If even one letter (or base) in that manual gets changed, it can sometimes change what protein gets made — which might affect how your body works. Mutations can happen by accident when cells copy DNA, or because of things like sunlight or chemicals.

So, simple answer:
→ A mutation is a change in the DNA sequence.

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Question 2: Which part of the DNA experiences the mutation?

The question says: “A specific part of a nucleic acid (such as DNA or RNA) experiences a mutation...” and asks which part of the DNA changes.

In DNA, the parts that carry the actual code are the nitrogenous bases: Adenine (A), Thymine (T), Cytosine (C), and Guanine (G). These bases pair up (A with T, C with G) and form the “rungs” of the DNA ladder. When we talk about mutations changing proteins, we’re usually talking about a change in one of these bases — especially in the sequence that codes for amino acids.

So, the part of DNA that experiences the mutation is:
→ The nitrogenous base (or just “base”) — specifically, the sequence of bases that makes up a gene.

But since the question refers to the illustration below (which shows two DNA strands with colored rungs), and asks which *part* of the DNA experiences the mutation — the best answer is:

→ One of the base pairs (the colored rungs in the DNA ladder).

More precisely:
→ The specific base (like A, T, C, or G) that gets swapped out.

Final short answer for #2:
→ The nitrogenous base (or base pair) in the DNA sequence.

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Question 3: Draw an arrow on the DNA illustration to show where the answer to #2 could be located.

Since you can’t draw here, I’ll describe exactly where to put the arrow.

Look at the DNA illustration — there are two DNA double helixes side by side. Each has colored blocks representing base pairs (like red-blue, green-yellow, etc.).

You should draw an arrow pointing to one of the colored blocks (base pairs) along the strand — any one will do, since a mutation can happen anywhere in the sequence.

For example: Point to the topmost colored block on the left DNA strand. That represents one base pair — if that base changed, it would be a mutation.

So, in words:
→ Draw an arrow pointing to any single colored rung (base pair) in either DNA molecule shown.

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Question 4: The mRNA codon CUU could mutate to C______ and still code for leucine...

We need to find another mRNA codon that starts with “C” and still codes for leucine.

First, remember: mRNA codons are read in groups of 3 letters. Each codon tells the cell which amino acid to add to a protein.

Leucine is coded by several different codons. From the standard genetic code:

Leucine codons include:
- UUA
- UUG
- CUU
- CUC
- CUA
- CUG

So, if the original codon is CUU, and we want to change only the last letter (to make it a silent mutation — same amino acid), we can change it to:

→ CUC, CUA, or CUG

All of those still code for leucine!

The question says: “mutate to C______” — so they want us to fill in the blank after “C”.

Any of those three work. Let’s pick CUC — it’s very similar to CUU (only the last letter changes from U to C).

Also, note: In the little yellow circle in the image, it says “Leucine (mRNA CUU)” — and then there’s a blank: “could mutate to C_____”. So they’re hinting that we keep the first two letters “CU” and change the third.

Perfect — so CUC, CUA, or CUG all work.

Let’s choose CUC as the answer — it’s common and easy.

Wait — let me double-check using the codon chart logic:

Original: CUU → Leucine
Change third base:
- CUC → still Leucine ✔
- CUA → still Leucine ✔
- CUG → still Leucine ✔

Yes! All good.

So final answer for #4:
→ CUC (or CUA or CUG — but we’ll go with CUC)

Actually, looking back at the text box near the yellow face:
“The mRNA codon CUU could mutate to C______ and still code for Leucine…”

And in question 4 on the right:
“The mRNA codon CUU could mutate to C______ and still code for leucine…”

They both have the same blank. So we just need to fill in the missing two letters after “C”.

Best choice: CUC

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Now, let’s compile all answers clearly.

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Final Answer:

1. A mutation is a change in the DNA sequence.

2. The nitrogenous base (or base pair) in the DNA sequence.

3. [Draw an arrow pointing to any single colored rung/base pair in the DNA illustration.]

4. CUC