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Year 10
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Mutations and genetic variants

I can explain how mutations in DNA cause genetic variants.

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Year 10
Edexcel
Higher

Mutations and genetic variants

I can explain how mutations in DNA cause genetic variants.

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Lesson details

Key learning points

  1. A change in the sequence of nucleotide bases in the DNA of the genome is called a mutation.
  2. Mutations can be caused by some substances and by ionising radiation.
  3. Most mutations are caused by errors when DNA is copied, when cells divide to make new cells.
  4. How substitution, insertion and deletion mutations change the base sequence in DNA.
  5. A mutation creates a genetic variant (a region of DNA in which the sequence of nucleotide bases has been changed).

Keywords

  • DNA - DNA is a large chemical molecule made of smaller chemical groups. It carries the genetic code of all living organisms.

  • Nucleotide - Nucleotides are the chemical groups that are the building blocks of DNA. The four types are coded A, T, C and G.

  • Mutation - A mutation is a change in the nucleotide base sequence in the DNA of the genome.

  • Ionising radiation - Ionising radiation (e.g. X-rays, gamma rays and high-energy ultraviolet) can cause mutations in DNA.

  • Genetic variant - A genetic variant is produced when a mutation causes a change in the genetic sequence of a gene or a non-coding region of DNA.

Common misconception

Mixing up amino acids and nucleotides, also nucleotides and bases.

Activity checks: Nucleotides contain a base; DNA is a polymer of nucleotides that codes for the order of amino acids in a protein.


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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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Starter quiz

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6 Questions

Q1.
DNA has two nucleic acid chains, each made from nucleotides. The chains are held together because subunits of the nucleotides pair up. Which subunits of a nucleotide molecule pair up?
Correct Answer: bases, base, nucleotide bases, nucleotide base, nitrogenous base
Q2.
True or false? An mRNA molecule has two nucleic acid strands.
true
Correct answer: false
Q3.
Which of these statements is true?
Transcription and translation take place in the nucleus.
Transcription and translation take place on ribosomes.
Only translation takes place in the nucleus.
Correct answer: Only translation takes place on a ribosome.
Q4.
The protein myoglobin is found in muscles and is made from a chain of 153 amino acids. How many nucleotide bases code for this chain of amino acids?
Correct Answer: 459
Q5.
Which of these statements is true?
There are 64 triplet codes for 64 amino acids.
There are 20 triplet codes for 64 amino acids.
Correct answer: There are 64 triplet codes for 20 amino acids.
These are 20 triplet codes for 20 amino acids.
Q6.
The table shows the four triplet codes that code for the amino acid Val. A change to which of the three bases could cause this triplet to code for an amino acid other than Val?
An image in a quiz
First base only.
Correct answer: First and second bases only.
Second and third bases only.
All three bases.

Exit quiz

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6 Questions

Q1.
What is the best description of the genetic code?
The sequence of amino acids in a protein.
The sequence of nucleotides bases in a protein.
The sequence of amino acids in DNA.
Correct answer: The sequence of nucleotide bases in DNA.
Q2.
This is part of a genetic code: TAC CAG TCA CAG. A mutation changes the code to TAC CAT TCA CAG. What kind of mutation has taken place?
Correct Answer: substitution
Q3.
Who best describes a genetic variant?
Andeep: “A region of non-coding DNA.”
Correct answer: Aisha: “A region of DNA in which the nucleotide base sequence has changed.”
Jacob: “A non-functional protein.”
Lucas: “A protein in which the amino acid sequence has changed.”
Q4.
Match each word to its correct meaning.
Correct Answer:mutation,a change in the nucleotide base sequence in the genome
tick

a change in the nucleotide base sequence in the genome

Correct Answer:chemical mutagen,a substance that can cause changes to DNA
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a substance that can cause changes to DNA

Correct Answer:high-energy ultraviolet,a type of ionising radiation that can cause changes to DNA
tick

a type of ionising radiation that can cause changes to DNA

Correct Answer:nucleic acid,a chain of nucleotides joined together
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a chain of nucleotides joined together

Q5.
Mutations change the genetic code in a gene. A change to the gene can change the structure of the that is made when the code is read.
Correct Answer: protein, mRNA, messenger RNA, messenger ribonucleic acid, polypeptide
Q6.
Deletion mutations have a greater effect on the genetic code than substitution mutations. Why?
Correct answer: Deletion mutations remove a base from a triplet code.
Deletion mutations add a base to a triplet code.
Deletion mutations change every triplet code before the mutation.
Correct answer: Deletion mutations change every triplet code after the mutation.
Deletion mutations swap one base for another in a triplet code.