DNA and the Genome
Get to grips with DNA and the Genome for GCSE Biology with this free worksheet and full mark scheme — Foundation and Higher exam-style questions with worked answers for AQA, Edexcel and OCR. DNA is a polymer of two strands coiled into a double helix, and the genome is an organism's entire genetic material.
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These worksheets and mark schemes are original, written for Virtus Academy and checked against the current AQA, Edexcel and OCR specifications. Every worksheet comes with a full mark scheme.
Topic overview
DNA is the polymer that makes up chromosomes. It is a double helix made of two strands, and it contains the instructions for making all the proteins in an organism.
A gene is a small section of DNA on a chromosome, and each gene codes for a particular sequence of amino acids. Those amino acids join together to make a specific protein.
The genome is the entire genetic material of an organism. The whole human genome has been studied, which has already brought benefits: it helps in the search for genes linked to disease, in understanding and treating inherited disorders, and in tracing human migration patterns from the past.
Revision notes
DNA structure
DNA is a polymer made of two strands forming a double helix.
It is contained in structures called chromosomes, found in the nucleus. DNA carries the code for making proteins.
Genes and proteins
A gene is a small section of DNA on a chromosome.
Each gene codes for a particular sequence of amino acids, which join together to make a specific protein. Different proteins give cells their different structures and functions.
The genome and its uses
The genome is the entire genetic material of an organism.
Studying the human genome helps to search for genes linked to different types of disease, to understand and treat inherited disorders, and to trace human migration patterns from the past.
Key points
- DNA is a polymer forming a double helix.
- Chromosomes are made of DNA and found in the nucleus.
- A gene is a small section of DNA.
- Each gene codes for a sequence of amino acids.
- The genome is the entire genetic material of an organism.
- Studying the genome helps identify disease genes.
Worked examples
Example 1
Define a gene. [2 marks]
Model answer
A gene is a small section of DNA on a chromosome (1 mark) that codes for a particular sequence of amino acids to make a specific protein (1 mark).
Example 2
Give two benefits of understanding the human genome. [2 marks]
Model answer
It helps in the search for genes linked to different types of disease (1 mark), and it helps in understanding and treating inherited disorders (1 mark).
Example 3
Describe the structure of DNA. [2 marks]
Model answer
DNA is a polymer made up of two strands (1 mark) forming a double helix (1 mark).
Common mistakes
Saying DNA and a gene are the same.
A gene is a small section of the DNA molecule.
Saying the genome is one chromosome.
It is the entire genetic material of the organism.
Forgetting the amino acid step.
Genes code for amino acid sequences, which then form proteins.
Describing DNA as a single strand.
It has two strands twisted into a double helix.
Exam tips
- Include both the DNA section and the protein in your definition of a gene.
- Say double helix and two strands when describing structure.
- Learn the three genome benefits as a set.
- Keep DNA, gene, chromosome and genome clearly distinguished.
Key terms
- DNA
- The polymer carrying the genetic code, forming a double helix.
- Gene
- A section of DNA coding for a specific protein.
- Genome
- The entire genetic material of an organism.
- Amino acid
- The unit from which proteins are built.
Related topics
Written and reviewed against the current AQA, Edexcel and OCR specifications. Spotted an error? Let us know.