Mutations
Introduced| English | Meaning |
|---|---|
| mutation/mjuːˈteɪʃn/ | A change in genetic material, such as a DNA sequence or chromosome structure. |
| substitution/ˌsʌbstɪˈtjuːʃn/ | A mutation in which one nucleotide or base pair is replaced by another. |
| deletion/dɪˈliːʃn/ | A mutation in which one or more nucleotides are lost from a DNA sequence. |
| insertion/ɪnˈsɜːʃn/ | A mutation in which one or more nucleotides are added to a DNA sequence. |
| mutagen/ˈmjuːtədʒn/ | mutagen |
Mistakes in the code
- Copying billions of DNA bases is astonishingly accurate — but not perfect.
- Once in a while, a base gets changed.
- Such a change to the DNA is called a mutation.
- Mutations can be harmful, harmless, or, rarely, a lucky improvement.
What a mutation is
- A mutation 突变 is a change in the DNA base sequence.
- Because the sequence codes for proteins, a mutation can change a protein.
- A changed protein may work differently — or not at all.
- Even a single base swapped can matter.
Substitution 替换, deletion 缺失, and insertion 插入 mutations
A mutation is…
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A mutation is a change in the DNA sequence, which can change the protein a gene makes.
Types of mutation
- A substitution swaps one base for another.
- An insertion adds an extra base into the sequence.
- A deletion removes a base.
- Insertions and deletions shift the reading frame, often disrupting the whole protein.
A substitution mutation is when…
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A substitution swaps one base for another; insertions and deletions add or remove bases.
Effects and causes
- Many mutations have no effect at all — they are neutral.
- Some are harmful; a rare few are beneficial.
- Beneficial mutations provide the variation that drives evolution.
- A mutagen 诱变剂 — UV light, radiation, or some chemicals — raises the mutation rate.
Helpful, harmful, or neutral?
Sort each mutation by its effect - many do nothing, some harm, and a few help.
A factor that increases the mutation rate, like UV light, is a ____.
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A mutagen — UV light, radiation, or certain chemicals — makes mutations more likely.
All mutations are harmful.
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False. Many mutations are neutral and a few are beneficial; these provide the variation that drives evolution.
Select all true statements about mutations.
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Not every mutation is harmful — many are neutral and some are beneficial. The other three are correct.
Not every mutation is bad. Most are neutral, some are harmful, and a rare few are beneficial — and those helpful changes are the raw material of evolution. Do not assume "mutation" always means damage.
One base, a big difference:
- Sickle-cell disease comes from a single substitution in the haemoglobin gene.
- That one changed base makes a faulty haemoglobin, harming red blood cells.
- Yet the same allele also protects against malaria — the very same mutation can be both harmful and helpful.
A mutation is a change in the DNA base sequence. Types include substitution (swap a base), insertion (add one), and deletion (remove one). Mutations can be harmful, neutral, or beneficial, and a mutagen raises their rate. Beneficial mutations supply the variation for evolution.
Write from a frameshift
- One base is deleted from the coding sequence of a gene.
- The deletion is not a multiple of three.
What kind of mutation is this?
Codons are read in threes, so one missing base shifts the groups.
What is a deletion of one coding base?
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The reading frame changes downstream.