GCSE BiologyAQA, Edexcel and OCR
40 biology questions on inheritance, variation and evolution. Pick your answer, then tap to see if you were right and why. Every answer comes from the Show Working science bank, checked against the GCSE content every board in England teaches.
01 / Quiz yourselfTry it, then tap to check
Choose your answer before you open it. Then read why, so it sticks.
01 / Inheritance, variation and evolutionBoth tiers
Answer: B a double helix
DNA is a polymer: a long molecule built from many repeating units. It has two strands twisted around each other, a shape called a double helix.
Checked against OpenStax Biology 2e, 14.2 DNA Structure and Sequencing
02 / Inheritance, variation and evolutionBoth tiers
Answer: D all of its genetic material
The genome is the entire genetic material of an organism: every gene and all the DNA between them. The whole human genome has now been read.
Checked against OpenStax Biology 2e, 17.5 Genomics and Proteomics
03 / Inheritance, variation and evolutionBoth tiers
Answer: A a sex cell, such as a sperm or egg
Gametes are sex cells: sperm and eggs in animals, pollen and egg cells in flowering plants. They have half the usual number of chromosomes (23 in humans), so fertilisation restores the full set.
Checked against OpenStax Biology 2e, 11.1 The Process of Meiosis
04 / Inheritance, variation and evolutionBoth tiers
Answer: C a long DNA molecule carrying many genes
A chromosome is a long molecule of DNA, coiled up, carrying many genes. Human body cells have 23 pairs, with one chromosome of each pair from each parent.
Checked against OpenStax Biology 2e, 13.1 Chromosomal Theory and Genetic Linkage
05 / Inheritance, variation and evolutionBoth tiers
Answer: D a section of DNA that codes for a protein
A gene is a small section of DNA on a chromosome. Each gene codes for a particular sequence of amino acids, which makes a specific protein.
Checked against OpenStax Biology 2e, 15.1 The Genetic Code
06 / Inheritance, variation and evolutionBoth tiers
Answer: D a different version of the same gene
Alleles are different versions (variants) of the same gene, such as for different fur colours. You usually get one allele of each gene from each parent.
Checked against OpenStax Biology 2e, 12.2 Characteristics and Traits
07 / Inheritance, variation and evolutionBoth tiers
Answer: A one that is expressed even if only one copy is present
A dominant allele shows in the phenotype even with only one copy. A recessive allele shows only when there are two copies and no dominant allele. Dominant does not mean more common or better.
Checked against OpenStax Biology 2e, 12.2 Characteristics and Traits
08 / Inheritance, variation and evolutionBoth tiers
Answer: B having two identical alleles of a gene
Homozygous means the two alleles of a gene are the same (BB or bb). Heterozygous means they are different (Bb).
Checked against OpenStax Biology 2e, 12.2 Characteristics and Traits
09 / Inheritance, variation and evolutionBoth tiers
Answer: C the alleles an organism has
The genotype is the alleles present, such as Tt. The phenotype is the characteristic they produce, such as tall. Words like heterozygous describe a genotype, not a phenotype.
Checked against OpenStax Biology 2e, 12.2 Characteristics and Traits
10 / Inheritance, variation and evolutionBoth tiers
Answer: A differences in their environment, such as diet
The phenotype develops from the genome interacting with the environment. Height depends on genes but also on diet and health, which is why identical twins can still differ.
Checked against OpenStax Biology 2e, 12.2 Characteristics and Traits
11 / Inheritance, variation and evolutionBoth tiers
Answer: D by finding genes linked to diseases
Knowing the human genome lets scientists find genes linked to diseases and understand inherited disorders, leading to better tests and treatments. It does not mean every disorder can be cured yet.
Checked against OpenStax Biology 2e, 17.5 Genomics and Proteomics
12 / Inheritance, variation and evolutionBoth tiers
Answer: D to find the chance of passing it on
Genetic tests read parts of a person’s DNA. They help diagnose rare inherited conditions and some cancers, and show the risk of passing a condition on to children.
Checked against NHS website, Genetic and genomic testing
13 / Inheritance, variation and evolutionBoth tiers
Answer: B a characteristic controlled by one gene
Some features depend on a single gene with dominant and recessive alleles. Two unaffected parents can have an affected child if each carries one recessive allele: both are heterozygous carriers.
Checked against NHS website, Cystic fibrosis: causes
14 / Inheritance, variation and evolutionBoth tiers
Answer: B 3 : 1
A Punnett square for Aa × Aa gives AA, Aa, Aa and aa. Three of the four show the dominant phenotype, so the ratio is 3 : 1, and the chance of aa is 1 in 4, or 25%.
Checked against NHS website, Cystic fibrosis: causes
15 / Inheritance, variation and evolutionBoth tiers
Answer: A a half (50%)
Bb × bb gives Bb, Bb, bb and bb, so half the offspring are expected to be bb. TT × tt can only give Tt, so every offspring is heterozygous and shows the dominant feature.
Checked against OpenStax Biology 2e, 12.1 Mendel’s Experiments and the Laws of Probability
16 / Inheritance, variation and evolutionBoth tiers
Answer: B 1 in 4
Each fertilisation is a separate chance event, so earlier children do not change the odds. For two carriers the chance is 1 in 4 every time.
Checked against OpenStax Biology 2e, 12.1 Mendel’s Experiments and the Laws of Probability
17 / Inheritance, variation and evolutionBoth tiers
Answer: A many genes acting together
A few features, such as some inherited disorders, depend on a single gene. Most, like height, result from many genes interacting, often with the environment as well.
Checked against OpenStax Biology 2e, 12.2 Characteristics and Traits
18 / Inheritance, variation and evolutionBoth tiers
Answer: C XY
Human body cells have 23 pairs of chromosomes. One pair decides sex: females have two of the same (XX) and males have two different ones (XY).
Checked against OpenStax Biology 2e, 13.1 Chromosomal Theory and Genetic Linkage
19 / Inheritance, variation and evolutionBoth tiers
Answer: D either an X or a Y
Every egg carries an X. Half of all sperm carry an X and half a Y, so a genetic cross gives XX and XY in equal numbers: a 50% chance of a boy each time.
Checked against OpenStax Biology 2e, 13.1 Chromosomal Theory and Genetic Linkage
20 / Inheritance, variation and evolutionBoth tiers
Answer: C a lot
Members of a species usually differ a lot in their alleles. This variation comes from mutations and is reshuffled by sexual reproduction, and it is what natural selection acts on.
Checked against OpenStax Biology 2e, 19.1 Population Evolution
21 / Inheritance, variation and evolutionBoth tiers
Answer: C mutations
All variants arise from mutations, which are changes in DNA. Most have no effect on the phenotype, some influence it, and very few decide a characteristic on their own.
Checked against OpenStax Biology 2e, 19.1 Population Evolution
22 / Inheritance, variation and evolutionBoth tiers
Answer: A a change in the inherited characteristics of a population over time
Evolution is a change in the inherited characteristics of a population over many generations, through natural selection. Individuals do not evolve; populations do. Over time it can produce new species.
Checked against OpenStax Biology 2e, 18.1 Understanding Evolution
23 / Inheritance, variation and evolutionBoth tiers
Answer: C Individuals with it survive and breed more
Variants that suit the environment help individuals survive and breed, so their alleles are passed on more often. Over many generations those alleles become more common in the population.
Checked against OpenStax Biology 2e, 18.1 Understanding Evolution
24 / Inheritance, variation and evolutionBoth tiers
Answer: D Dark moths become more common
Dark moths are eaten less, so more of them survive to breed and pass on the allele for dark colour. No moth changes colour in its lifetime; the population changes.
Checked against OpenStax Biology 2e, 19.1 Population Evolution
25 / Inheritance, variation and evolutionBoth tiers
Answer: D Parts are replaced by minerals as they decay
Fossils form from parts that do not decay, from parts replaced by minerals as they decay, or as traces such as footprints and burrows. Soft-bodied organisms rarely fossilise, and many fossils were destroyed by geological activity.
Checked against OpenStax Biology 2e, 18.1 Understanding Evolution
26 / Inheritance, variation and evolutionBoth tiers
Answer: A They show how organisms changed over time
Fossils in rocks of different ages show how much, or how little, organisms have changed as life developed on Earth. They also show extinct organisms that are related to living ones.
Checked against OpenStax Biology 2e, 18.1 Understanding Evolution
27 / Inheritance, variation and evolutionBoth tiers
Answer: B A random mutation gives some resistance
Mutations happen at random. A resistant bacterium survives the antibiotic while others die, then reproduces, so the resistant strain spreads. Bacteria become resistant, not immune.
Checked against NHS website, Antibiotic resistance
28 / Inheritance, variation and evolutionBoth tiers
Answer: C Bacteria breed fast, so we can watch it happen
Bacteria reproduce very quickly, so natural selection by antibiotics can be seen within years rather than millions of years. Resistant strains such as MRSA are evolution happening now.
Checked against OpenStax Biology 2e, 22.4 Bacterial Diseases in Humans
29 / Inheritance, variation and evolutionBoth tiers
Answer: B They are grouped by how alike their DNA is
Organisms were first grouped by features you could see. Better microscopes revealed internal structures, and now DNA and other chemical evidence show how closely species are related, so some groups have changed.
Checked against OpenStax Biology 2e, 20.3 Perspectives on the Phylogenetic Tree
30 / Inheritance, variation and evolutionBoth tiers
The right order:
In selective breeding, humans choose parents with a useful feature, breed them, then breed the best offspring again, generation after generation, until all the offspring show the feature.
Checked against OpenStax Biology 2e, 19.3 Adaptive Evolution
31 / Inheritance, variation and evolutionBoth tiers
Answer: A inbreeding can make a breed prone to disease
Humans have bred crops and animals for useful features, like disease resistance or more milk, for thousands of years. Breeding close relatives reduces variation, so a breed can be prone to disease or inherited defects.
Checked against OpenStax Biology 2e, 19.3 Adaptive Evolution
32 / Inheritance, variation and evolutionBoth tiers
Answer: A changing an organism’s genome to give a useful feature
Genetic engineering changes an organism’s genome, often by adding a gene from another organism, to give a desired characteristic. Examples include bacteria that make human insulin and crops that resist pests.
Checked against OpenStax Biology 2e, 17.1 Biotechnology
33 / Inheritance, variation and evolutionHigher only
Answer: D something that carries the gene into a cell
Enzymes cut out the gene, which is put into a vector such as a bacterial plasmid or a virus. The vector carries it into the host cells, and cells are changed early in development so the organism grows with the gene.
Checked against OpenStax Biology 2e, 17.1 Biotechnology
34 / Inheritance, variation and evolutionBoth tiers
Answer: C higher yields from pest-resistant plants
GM crops can resist pests or herbicides and often give higher yields, and GM bacteria make medicines such as insulin. Scientists are also researching gene therapy to correct some inherited disorders.
Checked against OpenStax Biology 2e, 17.1 Biotechnology
35 / Inheritance, variation and evolutionBoth tiers
Answer: C their genes could spread to wild plants
Concerns include genes spreading to wild plants, harm to insects and the animals that eat them, unknown long-term effects of eating GM food, and ethical objections. Each use has to be weighed against its benefits.
Checked against OpenStax Biology 2e, 17.1 Biotechnology
36 / Inheritance, variation and evolutionBoth tiers
Answer: A when they can no longer breed to give fertile young
Members of one species can breed together to produce fertile offspring. If two populations are kept apart, natural selection can change them in different ways until they can no longer do this. They are then two separate species.
Checked against OpenStax Biology 2e, 18.2 Formation of New Species
37 / Inheritance, variation and evolutionBoth tiers · separate only
Answer: A No mate is needed, so it is fast
Asexual reproduction needs only one parent and no mate, so it is fast and saves time and energy. But the offspring are clones, so one disease or change in conditions can affect them all.
Checked against OpenStax Biology 2e, 43.1 Reproduction Methods
38 / Inheritance, variation and evolutionBoth tiers · separate only
Answer: C Variation helps a species survive change
Sexual reproduction mixes genes from two parents, so offspring vary. If the environment changes, some may survive and natural selection can act. But finding a mate takes time and energy, and it is slower.
Checked against OpenStax Biology 2e, 11.2 Sexual Reproduction
39 / Inheritance, variation and evolutionBoth tiers · separate only
Answer: A They multiply quickly but can still gain variation
Reproducing asexually lets numbers build up fast while conditions suit them. Reproducing sexually as well gives variation, which helps the species survive if conditions change.
Checked against OpenStax Biology 2e, 43.1 Reproduction Methods
40 / Inheritance, variation and evolutionBoth tiers · separate only
Answer: A a nucleotide
DNA is a polymer of four different nucleotides. Each has a common sugar and a phosphate group, with one of four bases (A, C, G or T) attached to the sugar. Sugar and phosphate alternate along each strand.
Checked against OpenStax Biology 2e, 14.2 DNA Structure and Sequencing
02 / Longer answersMarked by levels
Write your answer first, on paper. Then open it and tick off the points you made. How 6-mark questions are marked.
6 marks / How bacteria become resistantBoth tiers
In a population of bacteria there is variation, because mutations happen at random when the DNA is copied. By chance, one bacterium may have a mutation that makes it resistant to a particular antibiotic. The antibiotic does not cause this mutation; it is already there before the antibiotic is used. When a person takes the antibiotic, the bacteria without the mutation are killed, but the resistant bacteria survive. With the other bacteria gone there is less competition, so the resistant bacteria multiply and pass the gene for resistance on to their offspring. Bacteria can divide very quickly, as often as every 20 minutes in good conditions, so after many generations most of the population carries the resistance gene and the antibiotic no longer works. This is natural selection, because the individuals best suited to their environment, which now contains the antibiotic, survive and reproduce more. Antibiotic resistance is good evidence for evolution because we can actually observe the inherited characteristics of a population changing over a short time, exactly as Darwin’s theory predicts.
Saying the bacteria become “immune”, or that the antibiotic causes the mutation. Bacteria become resistant, and the mutation happens by chance before the antibiotic is used.
6 marks / Steps in genetic engineeringHigher only
First the gene for human insulin has to be isolated. A restriction enzyme is used to cut the insulin gene out of human DNA. The same restriction enzyme is used to cut open a plasmid, a small ring of DNA from a bacterium, which will act as the vector to carry the gene. Because the same enzyme is used, both the gene and the plasmid are left with matching sticky ends, which are short single-stranded sections of DNA with unpaired bases. The insulin gene is mixed with the cut plasmids, the sticky ends pair up, and the enzyme ligase joins the DNA together. The plasmid now contains the human gene. These plasmids are mixed with bacteria, and some of the bacteria take them up. The bacteria that have taken up the plasmid are selected, for example by using a plasmid that also carries a gene for antibiotic resistance and growing the bacteria on that antibiotic, so only bacteria with the plasmid survive. The modified bacteria are grown in a fermenter, where they divide many times. Each one follows the instructions in the human gene and makes human insulin, which is extracted and purified for people with diabetes.
Mixing up the enzymes: restriction enzymes cut DNA and ligase joins it. Also remember the gene is carried into the bacterium by a vector such as a plasmid.
6 marks / Sexual and asexual reproduction comparedBoth tiers · separate only
Strawberry plants can reproduce sexually by making seeds, and asexually by sending out runners that grow into new plants.
Reproducing asexually by runners needs only one parent, whereas making seeds needs flowers to be pollinated, which often depends on insects. Asexual reproduction is also faster and uses less time and energy, so when conditions are good a strawberry plant can quickly cover an area with new plants. However, the new plants are made by mitosis, so they are genetically identical to the parent. This is useful if the parent is well suited to the conditions, but it is a disadvantage if the environment changes. For example, if a new disease arrives, all the identical plants are likely to be affected. In sexual reproduction, seeds form from the fusion of male and female gametes made by meiosis, so the offspring show variation. Some of them may have features that help them survive a change, such as a new disease or a drought, so the species is more likely to survive through natural selection. Sexual reproduction is slower, because the flowers must be pollinated and the seeds must develop. However, seeds can be spread away from the parent plant, so the young plants compete less with it, whereas runners grow right next to the parent.
Writing about only one type of reproduction. A compare answer needs both sides, with words like “whereas” or “faster than”, and each advantage should be linked to why it matters.
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