GCSE Biology Topic 6: Inheritance, Variation and Evolution MCQs – 30 Practice Questions with Answers (AQA 8461)
Free practice for AQA GCSE Biology 8461 on inheritance, variation and evolution, covering reproduction, genes and genetic crosses, variation, natural selection, selective breeding and classification, with a short explanation after every question.
Reproduction, Chromosomes and Meiosis
Q1. How is a gene defined?
- (A) A whole chromosome
- (B) A cell that carries out photosynthesis using chloroplasts in its cytoplasm
- (C) A section of DNA that codes for a particular protein
- (D) A protein found only in gametes
Show Answer
Answer: C – A gene is a section of DNA that codes for a particular protein, and genes sit on chromosomes.
Q2. How many copies of each chromosome do most body cells carry, and where do they come from?
- (A) Two copies, one from each parent
- (B) One copy, from the mother only
- (C) Four copies, two from each parent
- (D) One copy, from the father only
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Answer: A – Most body cells carry two copies of each chromosome, one inherited from each parent.
Q3. What is the genome of an organism?
- (A) A single gene for eye colour
- (B) The set of proteins in one cell
- (C) The number of cells in an embryo at an early stage of development
- (D) The entire genetic material of that organism
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Answer: D – The genome is the entire genetic material of an organism, including all of its genes.
Q4. What happens during meiosis?
- (A) A cell divides once to make two identical cells, as happens in growth and repair
- (B) A cell divides to produce sex cells with half the usual number of chromosomes
- (C) Two cells fuse to form a zygote
- (D) A cell copies its DNA but does not divide
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Answer: B – Meiosis produces sex cells (gametes) with half the usual number of chromosomes.
Q5. Why does fertilisation restore the full chromosome number?
- (A) Two sex cells, each with half the number, fuse together
- (B) The egg cell divides twice before fusion
- (C) Chromosomes double during fertilisation
- (D) The sperm cell carries the full number already, so no further division is needed
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Answer: A – When two sex cells fuse at fertilisation, the full chromosome number is restored and the offspring carries a new combination of alleles.
Q6. Which type of reproduction produces offspring that are genetically identical to the parent?
- (A) Sexual reproduction
- (B) Cross-pollination
- (C) Fertilisation between two parents
- (D) Asexual reproduction
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Answer: D – Asexual reproduction involves only one parent, so the offspring are genetically identical clones of that parent.
Q7. What does the term allele mean?
- (A) A chromosome pair
- (B) A sex cell
- (C) One version of a gene
- (D) A protein made during digestion
Show Answer
Answer: C – An allele is one version of a gene; different alleles of the same gene can give different characteristics.
Genotype, Phenotype and Genetic Crosses
Q8. How do genotype and phenotype differ?
- (A) Genotype is the observable characteristic and phenotype is the alleles carried, reversing the two terms
- (B) Genotype describes the alleles carried, while phenotype is the observable characteristic
- (C) Genotype only applies to plants and phenotype only to animals
- (D) Genotype and phenotype are two names for the same thing
Show Answer
Answer: B – Genotype describes the alleles carried, and phenotype describes the observable characteristic that results from the genotype plus the environment.
Q9. An organism carries one dominant and one recessive allele for a gene. What is it called?
- (A) Homozygous dominant
- (B) Homozygous recessive, carrying two copies of the recessive allele
- (C) A gamete
- (D) Heterozygous for that gene
Show Answer
Answer: D – An organism with one dominant and one recessive allele is heterozygous for that gene.
Q10. When is a recessive allele expressed?
- (A) Only when two copies of it are present
- (B) Whenever one copy is present
- (C) Only in male organisms
- (D) Only when the dominant allele is absent from the population
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Answer: A – A recessive allele is only expressed when two copies are present, whereas a dominant allele is expressed even when only one copy is present.
Q11. Two heterozygous parents (Aa x Aa) have offspring. What is the expected ratio of phenotypes for a dominant characteristic?
- (A) 1 dominant : 1 recessive, as in a cross between a heterozygote and a recessive parent
- (B) 2 dominant : 2 recessive
- (C) 3 showing the dominant characteristic : 1 showing the recessive characteristic
- (D) 4 dominant : 0 recessive
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Answer: C – The offspring genotypes are 1 AA : 2 Aa : 1 aa, giving a 3 : 1 ratio of dominant to recessive phenotypes.
Q12. A heterozygous parent (Aa) is crossed with a homozygous recessive parent (aa). What is the expected phenotype ratio in the offspring?
- (A) 3 : 1
- (B) 1 : 1
- (C) 2 : 1
- (D) 1 : 0
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Answer: B – Crossing Aa with aa gives equal numbers of Aa and aa offspring, so the phenotype ratio is 1 : 1.
Q13. What is a Punnett square used for?
- (A) Predicting the possible genotypes and phenotypes of offspring from a cross
- (B) Counting chromosomes under a microscope
- (C) Measuring the rate of photosynthesis in leaves under different light intensities
- (D) Classifying organisms into kingdoms
Show Answer
Answer: A – A Punnett square shows the possible combinations of alleles in offspring and so predicts their possible genotypes and phenotypes.
Q14. In humans, which chromosome combination normally gives a female?
- (A) XY
- (B) YY
- (C) XO
- (D) XX
Show Answer
Answer: D – Females normally carry two X chromosomes (XX), while males normally carry one X and one Y chromosome (XY).
Q15. A genetic disorder is caused by a recessive allele. Two carrier parents (both heterozygous) have a child. What is the chance the child inherits the disorder?
- (A) 0 out of 4
- (B) 2 out of 4
- (C) 1 out of 4
- (D) 4 out of 4
Show Answer
Answer: C – From Aa x Aa, one offspring in four is expected to be aa and so to show the recessive disorder.
Variation, Mutation and Natural Selection
Q16. What causes variation within a species?
- (A) Identical genes in every individual
- (B) Differences in genes inherited, in environmental conditions, or in both combined
- (C) The same environment for every individual, removing all environmental effects on development
- (D) Asexual reproduction only
Show Answer
Answer: B – Variation may be due to differences in genes inherited, differences in the conditions in which organisms developed, or a combination of both.
Q17. Which of these is an example of variation caused mainly by the environment?
- (A) Blood group
- (B) Natural eye colour, determined by the alleles inherited from parents
- (C) Number of chromosomes
- (D) A scar left by an injury
Show Answer
Answer: D – A scar results from an event during life, so it is environmental variation, unlike inherited characteristics such as blood group.
Q18. How is a mutation defined?
- (A) A random change in DNA
- (B) The fusion of two gametes
- (C) The division of a cell into two identical cells
- (D) The transfer of a gene between species by humans
Show Answer
Answer: A – Mutations are random changes in DNA; most have little or no effect, a few are harmful, and a few give an advantage in a particular environment.
Q19. What does the theory of evolution by natural selection state about the origin of species?
- (A) Each species was created separately and has remained completely unchanged over long periods of time
- (B) Species change only because humans breed them
- (C) All species evolved from simple life forms that first developed over three billion years ago
- (D) New species appear fully formed without ancestors
Show Answer
Answer: C – The theory states that all species of living things have evolved from simple life forms that first developed more than three billion years ago.
Q20. Which sequence best describes natural selection?
- (A) All offspring survive equally, then the population stays the same
- (B) Organisms vary, more are produced than can survive, the best adapted reproduce, and their alleles spread
- (C) Organisms choose new alleles during their lifetime and pass those acquired alleles on to their offspring
- (D) The environment changes the genes of adult organisms directly
Show Answer
Answer: B – Natural selection works through variation, overproduction, survival of the best adapted, and the spread of advantageous alleles over generations.
Q21. When have two populations of one species formed two new species?
- (A) When they become so different that they can no longer interbreed to produce fertile offspring
- (B) When they live in different countries and rarely meet, even though they could still interbreed successfully
- (C) When one population is larger than the other
- (D) When they eat different foods for one season
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Answer: A – Two new species have formed when two populations become so different that they can no longer interbreed to produce fertile offspring.
Q22. How does antibiotic resistance in bacteria provide evidence for evolution?
- (A) Antibiotics change bacterial genes on purpose
- (B) All bacteria die equally when antibiotics are used
- (C) Bacteria learn to avoid antibiotics during their lifetime and pass that acquired learning on to offspring
- (D) Resistant bacteria survive treatment, reproduce, and pass resistance on, so resistant strains spread
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Answer: D – Resistant variants survive antibiotic treatment and reproduce, so over time the resistant characteristic becomes more common in the population.
Selective Breeding, Genetic Engineering and Classification
Q23. What is selective breeding?
- (A) Allowing organisms to breed at random
- (B) Cloning an organism in a laboratory
- (C) Humans choosing organisms with wanted characteristics and breeding from them over generations
- (D) Moving a gene from one species into another, which is genetic engineering rather than selective breeding
Show Answer
Answer: C – Selective breeding, or artificial selection, is when humans choose organisms with wanted characteristics and breed from them over many generations.
Q24. Which is a possible drawback of selective breeding?
- (A) It always increases genetic diversity, giving larger and healthier populations over time
- (B) It can reduce genetic diversity and increase the risk of inherited problems
- (C) It prevents any characteristic from changing
- (D) It makes all offspring identical clones
Show Answer
Answer: B – Repeatedly breeding from a small number of chosen organisms narrows the gene pool, which can reduce diversity and raise the risk of inherited defects.
Q25. How is genetic engineering defined?
- (A) Breeding animals with wanted characteristics over many generations, which is selective breeding not engineering
- (B) Studying fossils to date rocks
- (C) Classifying organisms by their appearance
- (D) Modifying the genome by introducing a gene from another organism to give a desired characteristic
Show Answer
Answer: D – Genetic engineering involves modifying the genome by introducing a gene from another organism, for example inserting the human insulin gene into bacteria.
Q26. Why are bacteria used to produce human insulin by genetic engineering?
- (A) Bacteria with the human insulin gene can produce human insulin in large amounts
- (B) Bacteria naturally make human insulin
- (C) Bacteria remove the need for any insulin treatment in people with diabetes, curing the condition
- (D) Bacteria cure diabetes permanently
Show Answer
Answer: A – Bacteria given the human insulin gene produce human insulin, which can then be collected and purified for treatment.
Q27. What evidence for evolution comes from fossils?
- (A) Fossils show only species alive today, with no record of extinct forms or of how life has changed
- (B) Fossils show organisms that lived long ago, including extinct species, and how life has changed
- (C) Fossils prove that species never change
- (D) Fossils are formed only from living plants
Show Answer
Answer: B – Fossils and the fossil record provide evidence for evolution, and extinct species such as dinosaurs are known mainly from fossils.
Q28. In the modern classification system, which group is the largest, containing many different organisms?
- (A) Species
- (B) Genus
- (C) Kingdom
- (D) Family
Show Answer
Answer: C – The classification hierarchy runs from kingdom (largest) down through phylum, class, order, family, genus to species (smallest).
Q29. What is the binomial name of an organism made up of?
- (A) Its kingdom and phylum, the two largest groups in classification
- (B) Its family and order
- (C) Its class and genus
- (D) Its genus and species names
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Answer: D – The binomial system names each organism using its genus followed by its species, giving a unique two-part scientific name.
Q30. Why did the understanding of genetics change how scientists classify organisms?
- (A) DNA evidence showed evolutionary relationships more reliably than appearance alone
- (B) Appearance became the only feature used
- (C) Fossils stopped being studied
- (D) All organisms were placed in a single kingdom, removing all other groups from classification
Show Answer
Answer: A – Comparisons of DNA, alongside other evidence, revealed evolutionary relationships that appearance alone could hide, reshaping classification.
Work through any questions you missed again, then revise those areas before moving on to the next topic.