When a mutation changes the sequence of nucleotide bases in a gene, this creates a genetic variant of the gene.
If a triplet code in a gene is changed, this may or may not change the amino acid sequence in the protein that is made.
A change in the amino acid sequence of a protein can change the 3D shape of the protein.
A change in the 3D shape of a protein can change what it does (e.g. by changing the shape of an enzyme’s active site).
These changes can have impacts on an organism’s phenotype.

Common misconception

Mutations always have a negative effect on an organism.

Mutations can produce variation in a phenotype by producing alleles of a gene.

Keywords

Gene - A gene is a section of DNA that holds the genetic code for a protein.
Genetic variant - A genetic variant is produced when a mutation causes a change in the genetic sequence of a gene or non-coding DNA.
Allele - A genetic variant in a gene creates an allele (a different version of the gene), which produces a different phenotype.
Triplet code - The triplet code is carried by genes. Each three nucleotide bases codes for a specific amino acid.
Phenotype - The phenotype is the physical characteristics of an organism.

Pupils can research phenotypes and look at multiple alleles in colour or changes that lead to genetic disorders.

Teacher tip

Licence

This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

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6 Questions

Q1.

Match each of the following to the correct number.

Correct Answer:1,the number of amino acids coded for by each triplet of bases

the number of amino acids coded for by each triplet of bases

Correct Answer:2,the number of nucleic acid strands in a DNA molecule

the number of nucleic acid strands in a DNA molecule

Correct Answer:3,the number of nucleotide bases in one triplet code

the number of nucleotide bases in one triplet code

Correct Answer:4,the number of different nucleotide bases found in DNA

the number of different nucleotide bases found in DNA

Q2.

If a single nucleotide base in DNA is swapped for another one, this is called a substitution .

Correct Answer: mutation

Q3.

What is the cause of most mutations in DNA?

chemical mutations in cigarette smoke

Correct answer: errors in copying DNA when cells divide

high-energy ultraviolet radiation

X-ray radiation

Q4.

This is part of a genetic code: TAC CAG TCA CAG. A mutation changes the code to TAC CAG TCC AG. What kind of mutation has taken place?

Correct Answer: deletion

Q5.

Insertion mutations have a greater effect on the genetic code than substitution mutations. Why?

Insertion mutations remove a base from a triplet code.

Correct answer: Insertion mutations add a base to a triplet code.

Insertion mutations change every triplet code before the mutation.

Correct answer: Insertion mutations change every triplet code after the mutation.

Insertion mutations swap one base for another in a triplet code.

Q6.

In which type of cell would a mutation have to happen if the mutation was to be inherited by a person’s offspring?

Correct answer: gamete cell

nerve cell

red blood cell

root hair cell

Q6 image 4 UYSEG

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6 Questions

Q1.

Which word means the physical characteristics of an organism?

genome

Correct answer: phenotype

polymer

ribosome

transcription

Q2.

A different version of a gene, created by a mutation, is called an .

Correct Answer: allele

Q3.

Match each word to its correct definition.

Correct Answer:gene,a section of DNA that holds the genetic code for a protein

a section of DNA that holds the genetic code for a protein

Correct Answer:genetic variant,a section of DNA in which a mutation has changed the base sequence

a section of DNA in which a mutation has changed the base sequence

Correct Answer:allele,a different version of a gene, created by a mutation

a different version of a gene, created by a mutation

Correct Answer:triplet code,a set of three nucleotide bases that codes for one amino acid

a set of three nucleotide bases that codes for one amino acid

Q4.

Match each mutation to the change it would cause in the amino acid sequence of the protein coded for by a gene.

Correct Answer:GAT mutated to GGT,would change leucine to proline

would change leucine to proline

Correct Answer:CAT mutated to CAA,no change in amino acid

no change in amino acid

Correct Answer:CAC mutated to GAC,would change valine to leucine

would change valine to leucine

Correct Answer:CAA mutated to GGA,would change valine to proline

would change valine to proline

Q5.

Put the steps in the correct order to describe how a mutation in a gene can change an organism’s phenotype.

1 - A mutation changes the sequence of bases in a gene.

2 - The gene is transcribed to make mRNA.

3 - Translation takes place at a ribosome, when tRNA joins amino acids together.

4 - The amino acid chain folds to make a protein.

5 - The protein folds differently because one or more amino acids has been changed.

6 - The protein structure is changed, so it might not work properly.

Q6.

Who identifies a mutation that is the most likely to result in a non-functional protein?

Izzy: “A substitution mutation in a gene.”

Correct answer: Jun: “A deletion mutation in a gene.”

Sam: “A substitution mutation in non-coding DNA.”

Sofia: “A mutagen in a gene.”