Starter quiz
- 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?
- 'bases' ✓
- True or false? An mRNA molecule has two nucleic acid strands.
- True
- False ✓
- 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.
- Only translation takes place on a ribosome. ✓
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- 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?
- '459' ✓
- Which of these statements is true?
- There are 64 triplet codes for 64 amino acids.
- There are 20 triplet codes for 64 amino acids.
- There are 64 triplet codes for 20 amino acids. ✓
- These are 20 triplet codes for 20 amino acids.
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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?- First base only.
- First and second bases only. ✓
- Second and third bases only.
- All three bases.
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Exit quiz
- 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.
- The sequence of nucleotide bases in DNA. ✓
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- 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?
- 'substitution' ✓
- Who best describes a genetic variant?
Andeep: “A region of non-coding DNA.”
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.”
- Match each word to its correct meaning.
- mutation⇔a change in the nucleotide base sequence in the genome ✓
- chemical mutagen⇔a substance that can cause changes to DNA ✓
- high-energy ultraviolet⇔a type of ionising radiation that can cause changes to DNA ✓
- nucleic acid⇔a chain of nucleotides joined together ✓
- 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.
- 'protein' ✓
- Deletion mutations have a greater effect on the genetic code than substitution mutations. Why?
- 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.
- Deletion mutations change every triplet code after the mutation. ✓
- Deletion mutations swap one base for another in a triplet code.
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Worksheet
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Presentation
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Video
Lesson Details
Key learning points
- A change in the sequence of nucleotide bases in the DNA of the genome is called a mutation.
- Mutations can be caused by some substances and by ionising radiation.
- Most mutations are caused by errors when DNA is copied, when cells divide to make new cells.
- How substitution, insertion and deletion mutations change the base sequence in DNA.
- A mutation creates a genetic variant (a region of DNA in which the sequence of nucleotide bases has been changed).
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.
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.
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