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Year 10
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Higher

The genetic code

I can describe how instructions for making proteins are coded into DNA.

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New
New
Year 10
OCR
Higher

The genetic code

I can describe how instructions for making proteins are coded into DNA.

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Share activities with pupils
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Lesson details

Key learning points

  1. DNA is a polymer of four different nucleotides (A, C, G and T).
  2. Proteins are polymers of amino acids.
  3. The sequence of nucleotides in a gene determines the order of amino acids in a protein.
  4. Each set of three nucleotides is a triplet code that corresponds to an amino acid, this code is universal.
  5. Different organisms have different sequences of nucleotides in their DNA, but share this common coding system.

Keywords

  • DNA - A large chemical molecule made of smaller chemical groups, it carries the genetic code of all living organisms.

  • Polymer - A chemical made up of smaller repeating chemical groups.

  • Protein - A chemical substance whose structure is coded for by the genetic code in genes.

  • Amino acid - A small chemical group that makes up a protein polymer, there are 20 types.

  • Nucleotide - A chemical group that make up the building blocks of DNA, the four types are coded A, T, C and G.

Common misconception

Genes, DNA and chromosomes are used interchangeably rather than understanding their separate definitions; also that organisms such as animals and plants are not related.

Use images to show the difference between DNA, genes and chromosomes; display a phylogenetic tree so the common ancestry of all living organisms can be visualised and so the commonality of DNA between all life.

Carry out a modelling activity with a code and sweets as amino acids so pupils can build different proteins from different genes, all using the same triplet codes.
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).

Lesson video

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Starter quiz

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6 Questions

Q1.
Starting with the largest, put the structures in order of decreasing size.
1 - cell
2 - nucleus
3 - genome
4 - chromosome
5 - gene
Q2.
What does the order of nucleotide bases in a gene determine?
the structure of a carbohydrate molecule
the structure of a fat molecule
the structure of the nucleus
Correct answer: the structure of a protein molecule
Q3.
What is the name of the type of molecule that acts as a catalyst in living organisms?
Correct Answer: enzyme, enzymes
Q4.
The diagram shows a single nucleotide. Which part of the nucleotide joins the two strands of a DNA molecule together?
An image in a quiz
Correct Answer: B, b, part B, part b
Q5.
One strand of a DNA molecule has the base sequence A A T C G A G C A. Which is the complementary base sequence on the other strand of the DNA molecule?
A A T C G A G C A
A C G A G C T A A
Correct answer: T T A G C T C G T
C C G A T C T A G
Q6.
The photograph shows a model of DNA made from jelly babies and liquorice sticks. In this model, which parts of the nucleotide molecules are represented by the liquorice sticks?
An image in a quiz
Bases only
Sugars only
Bases and sugars
Bases and phosphates
Correct answer: Sugars and phosphates

Exit quiz

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6 Questions

Q1.
Match each word to its meaning.
Correct Answer:DNA,a polymer that carries the genetic code for all living organisms

a polymer that carries the genetic code for all living organisms

Correct Answer:nucleotide,small chemical group; 4 types (ATCG) are joined together to make DNA

small chemical group; 4 types (ATCG) are joined together to make DNA

Correct Answer:polymer,long chain molecule made of small chemical groups joined together

long chain molecule made of small chemical groups joined together

Correct Answer:protein,a polymer that can be structural or functional, coded for by a gene

a polymer that can be structural or functional, coded for by a gene

Q2.
The diagram shows a nucleotide. DNA molecules have four types of nucleotides. Which sub units are the same in all four types?
An image in a quiz
A and B
Correct answer: A and C
B and C
A, B and C
Q3.
A gene is a section of DNA that codes for a particular protein. Each gene is a sequence of nucleotides. There are four different nucleotides. Which statement best describes how this code works?
Each nucleotide makes a different protein.
The number of nucleotides determines the protein.
Nucleotides on both DNA strands determine the protein.
Correct answer: Nucleotides on one DNA strand determines the protein.
Q4.
The genetic code is often described as a triplet code. Why?
Each nucleotide codes for three amino acids.
Three nucleotides code for a protein.
Three nucleotides code for three proteins.
Correct answer: Three nucleotides code for one amino acid.
Three nucleotides code for three amino acids.
Q5.
Put the statements in order, to describe how the nucleotides in a gene are the code for making a protein.
1 - A gene has a sequence of nucleotides.
2 - Each three nucleotides make up a triplet code.
3 - Each triplet code codes for one of 20 amino acids.
4 - The triplet code sequence determines the amino acid sequence.
5 - The amino acid sequence determines the structure of the protein.
Q6.
A protein is 21 amino acids long. How many nucleotides code for this chain of 21 amino acids?
7
21
42
Correct answer: 63