IGCSE Biology Topic 17: Inheritance MCQs – 30 Practice Questions with Answers (Cambridge 0610)

Free practice for Cambridge IGCSE Biology 0610 on inheritance, covering genes and chromosomes, mitosis and meiosis, monohybrid crosses, codominance and sex linkage. Every question comes with a worked explanation to help you master genetic diagrams and ratios.

Chromosomes, Genes and Proteins

Q1. What is a gene?

  • (A) A complete set of chromosomes in a cell
  • (B) A protein that speeds up a chemical reaction
  • (C) A length of DNA that codes for a protein
  • (D) A structure in the cytoplasm that makes lipids
Show Answer

Answer: C – Chromosomes are made of DNA, and each gene is a section of that DNA carrying instructions for one protein.

Q2. What is an allele?

  • (A) An alternative form of a gene
  • (B) A cell that contains two sets of chromosomes
  • (C) A protein found only in the nucleus
  • (D) A diagram used to predict the results of a cross
Show Answer

Answer: A – Different alleles of the same gene produce different versions of a trait, such as different flower colours.

Q3. How does the sequence of bases in a gene determine the protein that is made?

  • (A) The bases are copied directly into the finished protein.
  • (B) The bases decide how many chromosomes the cell will contain.
  • (C) The bases control whether the cell divides by mitosis or meiosis during growth.
  • (D) The base sequence sets the sequence of amino acids in the protein.
Show Answer

Answer: D – The order of bases is copied into messenger RNA, which then determines the order of amino acids assembled.

Q4. Why can two proteins with different amino acid sequences behave differently?

  • (A) They are always made in different types of cell at different stages of growth.
  • (B) Different amino acid sequences give the proteins different shapes.
  • (C) They contain different numbers of chromosomes.
  • (D) They are made only during cell division.
Show Answer

Answer: B – A protein’s shape decides how it works, so a changed sequence can change its function.

Q5. What is the role of messenger RNA (mRNA) in making a protein?

  • (A) It is a copy of a gene, made in the nucleus, that moves to the cytoplasm.
  • (B) It is a copy of a whole chromosome that stays inside the nucleus.
  • (C) It is an enzyme that digests proteins in the cytoplasm.
  • (D) It is a strand of DNA that replaces the gene after the protein is made in the cell.
Show Answer

Answer: A – The gene itself stays in the nucleus; the mRNA copy carries its instructions out to the ribosomes.

Q6. What happens at a ribosome during protein synthesis?

  • (A) DNA is copied to form two identical chromosomes before the cell divides.
  • (B) Amino acids are broken down into glucose.
  • (C) Amino acids are assembled into a protein in the order set by the mRNA.
  • (D) Messenger RNA is changed back into a gene.
Show Answer

Answer: C – As the mRNA passes through the ribosome, amino acids are joined in the sequence its bases specify.

Q7. Most body cells contain the same genes, yet a muscle cell and a skin cell make different proteins. Why?

  • (A) Each cell loses the genes it does not need as it matures into its final specialised form.
  • (B) Each cell gains new genes from neighbouring cells.
  • (C) Each cell copies only the genes for its own proteins.
  • (D) Many genes are not expressed in a given cell; it only makes the proteins it needs.
Show Answer

Answer: D – DNA controls cell function by controlling protein production, including enzymes, membrane carriers and receptors.

Q8. What does it mean if a nucleus is haploid?

  • (A) It contains two sets of chromosomes, one from each parent.
  • (B) It contains a single set of chromosomes.
  • (C) It contains no chromosomes at all.
  • (D) It contains 23 pairs of chromosomes.
Show Answer

Answer: B – A diploid nucleus, by contrast, holds two sets, with a pair of each type of chromosome.

Mitosis and Meiosis

Q9. How many pairs of chromosomes are found in a human diploid cell?

  • (A) 23 pairs
  • (B) 46 pairs
  • (C) 12 pairs
  • (D) 23 chromosomes in total
Show Answer

Answer: A – A human diploid cell has 46 chromosomes arranged as 23 pairs.

Q10. What is mitosis?

  • (A) A reduction division that halves the chromosome number to form gametes
  • (B) The fusion of two gamete nuclei to form a zygote
  • (C) Nuclear division that gives rise to genetically identical cells
  • (D) The copying of a gene into messenger RNA
Show Answer

Answer: C – Mitosis keeps the chromosome number the same in each daughter cell.

Q11. Which of these is a role of mitosis?

  • (A) Producing gametes with half the chromosome number
  • (B) Creating new allele combinations through random fertilisation and independent assortment.
  • (C) Changing the base sequence of a gene
  • (D) Growth, repair of damaged tissues and replacement of worn-out cells
Show Answer

Answer: D – Mitosis also underpins asexual reproduction, where offspring are genetically identical to the parent.

Q12. What happens to chromosomes just before mitosis begins?

  • (A) They are halved so each daughter cell gets only one set of chromosomes.
  • (B) They are copied exactly, so each daughter cell can receive a full set.
  • (C) They are shuffled into new combinations.
  • (D) They leave the nucleus and enter the ribosomes.
Show Answer

Answer: B – Exact replication followed by separation of the copies maintains the chromosome number.

Q13. What is a stem cell?

  • (A) An unspecialised cell that divides by mitosis to form cells that can specialise
  • (B) A cell that can only divide by meiosis to produce genetically different gamete cells
  • (C) A specialised cell that has lost its nucleus
  • (D) A cell that contains only one set of chromosomes
Show Answer

Answer: A – Stem cells provide a source of new cells that later specialise for particular functions.

Q14. How does meiosis differ from mitosis in its outcome?

  • (A) Meiosis produces two genetically identical diploid cells, as in mitosis, for growth.
  • (B) Meiosis produces cells with double the chromosome number.
  • (C) Meiosis is a reduction division producing genetically different haploid cells.
  • (D) Meiosis produces cells that cannot divide again.
Show Answer

Answer: C – The chromosome number is halved from diploid to haploid, and the resulting cells differ genetically.

Q15. In which process is meiosis involved?

  • (A) Repair of a damaged leaf
  • (B) Growth of a root tip
  • (C) Replacement of dead skin cells
  • (D) Production of gametes
Show Answer

Answer: D – Gametes must be haploid so that fertilisation restores the diploid number in the zygote.


Monohybrid Inheritance

Q16. What is meant by the genotype of an organism?

  • (A) The observable features of the organism, including its height and eye colour.
  • (B) The genetic make-up of the organism, in terms of the alleles present
  • (C) The number of chromosomes in its gametes
  • (D) The pedigree chart of its ancestors
Show Answer

Answer: B – The phenotype, by contrast, is the observable result of that genetic make-up.

Q17. An organism carries two identical alleles of a particular gene. What term describes it?

  • (A) Homozygous
  • (B) Heterozygous
  • (C) Haploid
  • (D) Codominant
Show Answer

Answer: A – Two identical homozygous individuals that breed together are pure-breeding for that gene.

Q18. What is a dominant allele?

  • (A) An allele that is only expressed when two copies are present
  • (B) An allele that disappears from the population in one generation
  • (C) An allele that is expressed if it is present in the genotype
  • (D) An allele that is found only on a sex chromosome
Show Answer

Answer: C – A recessive allele, by contrast, is only expressed when no dominant allele of the gene is present.

Q19. A heterozygous plant is crossed with another heterozygous plant. Why will this plant not be pure-breeding?

  • (A) It carries only one allele of the gene.
  • (B) It produces no gametes at all.
  • (C) Its offspring are always genetically identical to it and to each other.
  • (D) It carries two different alleles, so offspring genotypes can differ.
Show Answer

Answer: D – Heterozygous parents can pass on either allele, giving varied offspring rather than a uniform pure line.

Q20. In pea plants, tall (T) is dominant to short (t). What phenotypic ratio is expected from a cross between two heterozygous tall plants (Tt x Tt)?

  • (A) 1 tall : 1 short
  • (B) 3 tall : 1 short
  • (C) 1 tall : 3 short
  • (D) All tall
Show Answer

Answer: B – The Punnett square gives TT, Tt, Tt and tt, so three quarters show the dominant tall phenotype.

Q21. A heterozygous tall pea plant (Tt) is crossed with a homozygous short plant (tt). What phenotypic ratio is expected?

  • (A) 1 tall : 1 short
  • (B) 3 tall : 1 short, as in a cross between two heterozygotes
  • (C) All tall
  • (D) All short
Show Answer

Answer: A – Half the offspring receive T and half receive only t, giving an equal split of phenotypes.

Q22. How can a test cross identify whether a tall pea plant is TT or Tt?

  • (A) Cross it with another tall plant and count the seeds produced in the next generation.
  • (B) Cross it with a plant of a different species.
  • (C) Cross it with a homozygous recessive (tt) plant and look for any short offspring.
  • (D) Examine its chromosomes under a microscope.
Show Answer

Answer: C – If any short offspring appear, the tall parent must have carried the recessive allele; if none appear in a large sample, it is likely TT.

Codominance, Blood Groups and Sex Linkage

Q23. A pedigree diagram shows a characteristic appearing in every generation and affecting both sexes roughly equally. What does this pattern most likely suggest?

  • (A) The characteristic is caused by a new mutation in each generation of the family independently.
  • (B) The characteristic is determined only by the environment.
  • (C) The characteristic is carried on the Y chromosome.
  • (D) The characteristic is inherited as a dominant allele passed from parent to offspring.
Show Answer

Answer: D – Pedigree diagrams trace how a characteristic passes through a family, and a dominant pattern appears in each generation.

Q24. What is codominance?

  • (A) A situation where the recessive allele masks the dominant allele completely in every generation.
  • (B) A situation where both alleles in a heterozygous organism contribute to the phenotype
  • (C) A situation where only one allele is present in the genotype
  • (D) A situation where alleles are lost during meiosis
Show Answer

Answer: B – In codominance neither allele is hidden, so the heterozygote shows features of both.

Q25. In ABO blood groups, which genotype gives blood group AB?

  • (A) IAIB
  • (B) IAIA, giving only the A antigen
  • (C) IBIo
  • (D) IoIo
Show Answer

Answer: A – The IA and IB alleles are codominant, so both are expressed in the AB phenotype.

Q26. Which genotype gives blood group O?

  • (A) IAIo
  • (B) IBIB
  • (C) IoIo
  • (D) IAIB
Show Answer

Answer: C – The Io allele is recessive, so group O appears only when no IA or IB allele is present.

Q27. In humans, which parent determines the sex of a child?

  • (A) The mother, because she always contributes a Y chromosome to the child.
  • (B) Neither parent, because sex is decided by the environment
  • (C) The mother, because she contributes two X chromosomes
  • (D) The father, because his sperm may carry an X or a Y chromosome
Show Answer

Answer: D – Females are XX and males are XY, so an X-bearing sperm gives a daughter and a Y-bearing sperm gives a son.

Q28. What is a sex-linked characteristic?

  • (A) A feature controlled by an allele on an autosome, inherited equally by both sexes.
  • (B) A feature whose gene is on a sex chromosome, so it is more common in one sex.
  • (C) A feature that only appears in the heterozygous genotype
  • (D) A feature that changes with the seasons
Show Answer

Answer: B – Because males have only one X chromosome, a recessive allele on it is expressed more often in males.

Q29. Red-green colour blindness is an example of sex linkage. Why is it more common in males than in females?

  • (A) Females do not carry the gene for colour vision at all.
  • (B) Males inherit two copies of the faulty allele, one from each parent, during fertilisation.
  • (C) A male needs only one copy of the recessive allele on his single X chromosome.
  • (D) The allele is carried on the Y chromosome only.
Show Answer

Answer: C – A female needs two copies of the recessive allele, one on each X chromosome, before it shows.

Q30. A woman who carries the allele for red-green colour blindness (XBXb) has children with a colour-blind man (XbY). What proportion of their sons is expected to be colour-blind?

  • (A) Half of the sons
  • (B) None of the sons
  • (C) All of the sons
  • (D) A quarter of the sons
Show Answer

Answer: A – Sons receive their X chromosome from their mother, so half receive Xb and are colour-blind, and half receive XB and have normal colour vision.

Revisit any questions you missed, especially the Punnett square ratios and the sex-linkage crosses, and try the set again until the patterns feel secure.