When a cell copies a gene to make mRNA (the instructions to make a protein), this is called gene expression.
Only around 1-2% of the genome is genes; the rest contains code that controls gene expression.
A genetic variant in a non-gene (so called "non-coding") section of the genome can affect gene expression.
Non-coding DNA affects gene expression because it is where RNA polymerase starts copying the gene for protein synthesis.
Genetic variants in non-coding DNA can impact gene expression and therefore an organism’s phenotype.

Common misconception

All DNA is genes that code for proteins; and that our characteristics are only affected by our genes

Most of the DNA is non-coding (non-genes), and controls when genes are expressed (i.e. when proteins are made). Changes (genetic variants) in non-coding DNA can affect characteristics (phenotype) as they control whether a gene is expressed or not.

Keywords

Gene - A section of DNA that holds the genetic code for a protein.
Protein - A chemical substance whose structure is coded for by the genetic code in genes.
Gene expression - The process in which genes are copied during the first step in protein synthesis.
Genetic variant - Produced when a mutation causes a change in the genetic sequence of a gene or non-coding section of DNA.
Phenotype - The physical characteristics of an organism.

Edit this slide deck dependant on exam board and ability. There is opportunity to research the role of epigenetics and new treatments for diseases once pupils understand that the expression of genes can be changed even though the base sequence within the genes stays the same.

Teacher tip

Equipment

None required.

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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Starter quiz

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6 Questions

Q1.

Match each word to its correct meaning.

Correct Answer:mutagen,Something capable of causing a change in the genetic code.

Something capable of causing a change in the genetic code.

Correct Answer:mutation, A change in the genetic code.

A change in the genetic code.

Correct Answer:transcription,The process of copying a gene and making mRNA.

The process of copying a gene and making mRNA.

Correct Answer:translation ,Using the genetic code of mRNA to make a polypeptide.

Using the genetic code of mRNA to make a polypeptide.

Q2.

Match the number to the description.

Correct Answer:four,The number of types of nucleotide base in DNA.

The number of types of nucleotide base in DNA.

Correct Answer:two,The number of nucleic acid strands in a molecule of DNA.

The number of nucleic acid strands in a molecule of DNA.

Correct Answer:one,The number of nucleic acid strands in a molecule of mRNA.

The number of nucleic acid strands in a molecule of mRNA.

Correct Answer:three,The number of nucleotide bases in a triplet code.

The number of nucleotide bases in a triplet code.

Q3.

Which of these is not a type of mutation?

deletion

Correct answer: division

insertion

substitution

Q4.

Allele 1 has mutated to become allele 2. Allele 1 code: ATT CCG GAC TAT ATA CGC CCC. Allele 2 code: ATT CGG GAC TAT TAT ACG CCC C. How many mutations have there been in allele 1

Correct Answer: 2, two

Q5.

Put the statements in order to describe how a gene in the nucleus is used to make an enzyme that controls a chemical reaction in the cytoplasm.

1 - A gene copy called mRNA is made in the nucleus.

2 - The copy is small enough to get into the cytoplasm.

3 - The sequence of bases in mRNA is read at a ribosome.

4 - Amino acids are assembled into a sequence determined by the mRNA base sequence.

5 - The amino acid sequence determines the 3D shape of the enzyme.

Q6.

A change in the 3D structure of a protein may lead to a change in an organism such as a different eye colour. What word do biologists use for physical characteristics such as eye colour?

Correct Answer: Phenotype, phenotype

Exit quiz

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6 Questions

Q1.

Genes are instructions to a cell on how to produce which type of molecule?

amino acids

mRNA

nucleotides

Correct answer: proteins

Q2.

DNA that isn’t used to determine the structure of a protein is called DNA.

Correct Answer: non-coding, noncoding, non coding

Q3.

What does the term 'gene expression' mean?

A gene codes for a protein using a nucleotide sequence.

Correct answer: A gene is activated so that the protein it codes for is produced.

RNA polymerase binds to the non-coding DNA before a gene.

The protein coded for by a gene is produced.

Q4.

Put the events in the synthesis of a protein in the correct order.

1 - A section of non-coding DNA activates a gene.

2 - RNA-polymerase enzyme binds to a section of non-coding DNA before the gene.

3 - mRNA copy of the gene is made.

4 - mRNA copy of the gene attaches to a ribosome and translation occurs.

5 - Amino acids join together in an order determined by the mRNA to form a protein.

Q5.

Changes to the non-coding DNA nucleotide sequence can happen due to copying errors or because of environmental factors such as chemicals in cigarette smoke. What are these changes to the DNA called?

Correct Answer: Mutations, mutations

Q6.

There are several ways changes to non-coding DNA can affect an organism's phenotype. Match the change to the description of how it can alter phenotype.

Correct Answer:Cell division genes are always activated,Cells constantly grow and divide leading to tumour formation.

Cells constantly grow and divide leading to tumour formation.

Correct Answer:Binding of RNA-polymerase is prevented.,Transcription is prevented and the protein can’t be produced.

Transcription is prevented and the protein can’t be produced.

Correct Answer:The activation of a gene is prevented.,Gene remains inactive and protein is not produced.

Gene remains inactive and protein is not produced.