AQA GCSE Combined Science Foundation (8464), Foundation tier · Biology › Inheritance, variation and evolution › Reproduction
Practise DNA and the genome. 6 exam-style questions on this subtopic, at up to four difficulty levels, with full mark schemes and a progress tracker. Free, no account needed.
What DNA, chromosomes, genes and the genome are, how a gene codes for a protein, and why studying the human genome matters. Expect short recall and 'put these in order of size' questions, plus 2 to 3 mark questions on how the human genome is useful.
Key facts
DNA = the genetic material in the nucleus
DNA = a polymer of two strands forming a double helix
Chromosome = structure that contains DNA
Gene = small section of DNA on a chromosome that codes for a particular sequence of amino acids, to make a specific protein
Genome = the entire genetic material of an organism
Human genome uses: genes linked to disease; understanding and treating inherited disorders; tracing past human migration
Notes
DNA, chromosomes and genes
diagram
The genetic material in the nucleus of a cell is a chemical called DNA.
DNA is a polymer made up of two strands forming a double helix.
DNA is contained in structures called chromosomes. Each chromosome contains one very long molecule of DNA.
A gene is a small section of DNA on a chromosome.
Each gene codes for a particular sequence of amino acids, to make a specific protein. Proteins such as enzymes control the characteristics of the organism.
In order of size: nucleus → chromosome → gene.
Nucleus → chromosome → gene → DNA (double helix).
The genome
The genome of an organism is the entire genetic material of that organism.
The whole human genome has now been studied. This will be very important for medicine in the future.
Why understanding the human genome matters
Searching for genes linked to different types of disease. People with a higher risk can be tested and treated or advised earlier.
Understanding and treating inherited disorders, such as cystic fibrosis, which could lead to better treatments.
Tracing human migration patterns from the past. Comparing the DNA of people from different parts of the world shows how groups are related and how early humans spread across the Earth.
How to answer each type of question
Recall: complete sentences or define the terms
1 to 4 marksGrade 4
Learn a one-line definition of DNA, chromosome, gene and genome.
Watch for distractors in a word box: gene and genome are easy to mix up.
Example. Complete the sentences using words from the box. [ chromosomes / double helix / gene / genome / protein ] DNA is a polymer made of two strands forming a ________. DNA is found in structures called ________. A ________ is a small section of DNA that codes for a specific ________. [4 marks]
Show the model answerHide the model answer
double helix (1); chromosomes (1); gene (1); protein (1)
Don’t lose marks
Saying a gene is bigger than a chromosome. A gene is a small section of the DNA on a chromosome.
Saying a gene codes for 'a characteristic' or for 'an amino acid'. It codes for a sequence of amino acids that makes a specific protein.
Confusing genome (all the genetic material) with gene.
Saying DNA is a single strand. It has two strands forming a double helix.
More tips
Memory tricks
Think of nesting boxes: the nucleus holds chromosomes, chromosomes are made of DNA, and genes are short sections of that DNA.
Gene = one instruction (for one protein); genome = the whole instruction book.
Uses of the human genome, 'DIM': Disease genes, Inherited disorders, Migration.
Exam technique
When asked how a gene affects a characteristic, go through the chain: gene → sequence of amino acids → protein → characteristic.
If asked for uses 'in medicine', don't give tracing human migration.
Use the words polymer and double helix when describing DNA.
What each grade needs
What you need to be able to do, from the first marks up to the top grade.
Grade 3
State where DNA is foundThe genetic material in the nucleus is a chemical called DNA, contained in chromosomes.
Grade 4
Describe the structure of DNA simplyDNA is a polymer made up of two strands forming a double helix.
Grade 4
Put nucleus, chromosome and gene in size orderNucleus (largest), then chromosome, then gene (a small section of DNA on a chromosome).
Grade 5
Define gene and genomeA gene is a small section of DNA on a chromosome; the genome is all of an organism's genetic material.
Quick recall
Cover the answers and test yourself. The app has these as flashcards that come back just before you'd forget them.
DNA is a polymer made of two strands. What name is given to the shape of a DNA molecule?
Double helix
The whole human genome has now been studied. What is meant by the genome of an organism?
The entire genetic material of that organism
Name the structures in a cell’s nucleus that contain most of an organism’s DNA.
Chromosomes
Sample questions
Written for this site in the style of AQA exam questions. They are not taken from real past papers.
Question 1Easy5 marks
The genetic material in the nucleus of a cell is found in chromosomes.
(a) What chemical is the genetic material in the nucleus made of? Tick (✓) one box.[1]
DNA
Glucose
Lipid
Starch
(b) DNA is a polymer made of two strands. What name is given to the shape of a DNA molecule?[1]
(c) Write the words chromosome, gene and genome in order of size, starting with the smallest.[1]
(d) What is a gene?[2]
Show the answer and mark scheme
(a)Answer: DNA
(b)Answer: Double helix
double helix
(c)Answer: Gene, chromosome, genome
gene, chromosome, genome
(d)Answer: A small section of DNA on a chromosome that codes for a particular sequence of amino acids, to make a specific protein
a (small) section of DNA (on a chromosome)
that codes for a particular sequence of amino acids / a specific protein
Question 2Medium7 marks
The whole human genome has now been studied.
(a) What is meant by the genome of an organism?[1]
(b) Give three reasons why studying the human genome is important.[3]
(c) Scientists found that women with a particular allele of one gene have a much higher risk of developing breast cancer. Suggest how this discovery could be used to help people.[2]
(d) Suggest one concern that people may have about genetic testing.[1]
Show the answer and mark scheme
(a)Answer: The entire genetic material of that organism
the entire / all the genetic material of the organism
(b)Answer: To search for genes linked to different types of disease; to understand and treat inherited disorders; to trace human migration patterns from the past
searching for genes linked to (different types of) disease
understanding and treatment of inherited disorders
tracing human migration patterns from the past
(c)Answer: Women could be tested for the allele; those with it could have more frequent check-ups or preventive treatment so any cancer is found early; drugs could be developed that target the faulty protein
people can be tested / screened for the allele
people with the allele can have regular check-ups / screening so cancer is detected early
people with the allele could choose preventive treatment / make lifestyle changes
new treatments / drugs could be developed that target the effects of the allele
(d)Answer: Insurance companies or employers might discriminate against people with a high-risk allele
discrimination by insurers / employers / anxiety about a result for a disease that may never develop / privacy of genetic data