IGCSE Biology (9–1) 0970 · Topic 17

Inheritance: past paper questions

193 real questionsasked in 9 of the last 10 exam series2019–2026usually: State, Complete, Describe, Explain, Define

Real questions on inheritance

The newest 20 of 92 written questions, plus 101 multiple-choice. Open one to see it on the real paper.

0970/31 · May/June 2026 · Q4a[3]
The list shows some words or phrases that can be used to describe the inheritance of albinism. Complete Table 4.1 using words or phrases from the list. Each word or phrase may be used once, more than once or not at all. dominant allele heterozygous homozygous phenotype recessive allele Table 4.1 example term Aa AA pale...
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0970/31 · May/June 2026 · Q4b[2]
Complete Table 4.2 by writing yes or no in each row to show if each pair of alleles results in albinism. Table 4.2 pair of alleles person has albinism (yes or no) AA Aa aa
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0970/31 · May/June 2026 · Q4c[2]
(c) People with the alleles AA and Aa have a baby. Complete the genetic diagram in Figure 4.1 to show the percentage chance of having a baby with the alleles Aa. A A A a percentage chance having baby with alleles .......... Figure 4.1
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0970/31 · May/June 2026 · Q4d(i)[1]
State where chromosomes are found in human cells.
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0970/31 · May/June 2026 · Q4d(ii)[1]
(ii) State the two sex chromosomes in humans. .......... eeeeeeeeeeeeeeeeeeeeeteeteetetetteetteteeees [1]
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0970/42 · May/June 2026 · Q5b(i)[3]
Describe the roles of mitosis in a root.
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0970/42 · May/June 2026 · Q5b(ii)[1]
Roots contain stem cells. Suggest the role of stem cells in a root.
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0970/32 · October/November 2025 · Q5a[2]
Describe what is meant by the term allele.
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0970/32 · October/November 2025 · Q5b[4]
Fig. 5.1 is a pedigree diagram for the inheritance of pod colour in some pea plants. Key green pod yellow pod 4 5 Fig. 5.1 6 7 3 2 1 The possible genotypes for pea pod colour are GG, Gg and gg. Determine the genotypes of individual 1 and individual 2 in Fig. 5.1. Explain how you determined your answer for each individu...
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0970/32 · October/November 2025 · Q5c[3]
Two pea plants with the genotype Gg for pod colour are bred together. Complete the Punnett square to determine the possible genotypes of the offspring and calculate the expected phenotypic ratio.
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0970/41 · May/June 2025 · Q3c[2]
Meiosis produces gametes and is a source of genetic variation. State two other sources of genetic variation in populations.
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0970/41 · May/June 2025 · Q3d[4]
Describe mitosis and its roles in organisms.
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0970/41 · May/June 2025 · Q3e[1]
State the name of the unspecialised cells that divide by mitosis.
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0970/41 · May/June 2025 · Q5a(iii)[2]
Suggest the groups with the most similar and least similar DNA base sequences to crocodiles in Fig. 5.1. most similar least similar
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0970/41 · May/June 2025 · Q5b[4]
Describe the structure of a DNA molecule.
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0970/41 · May/June 2025 · Q5c[3]
Outline how the base sequences in DNA control cell function.
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0970/42 · May/June 2025 · Q1c[5]
Cystic fibrosis is an inherited condition in humans caused by a recessive allele of a gene. There are two alleles for this gene: the allele for no cystic fibrosis is represented by the letter F the allele for cystic fibrosis is represented by the letter f. • • Two heterozygous parents wanted to have a child. parental p...
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0970/42 · May/June 2025 · Q3b(i)[1]
Genes are found at specific positions on a biological molecule. State the name of this biological molecule.
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0970/42 · October/November 2024 · Q3c(i)[2]
Describe what is meant by a gene mutation.
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0970/42 · October/November 2024 · Q5a[2]
State the number of people in Fig. 5.1 with: only one I A allele. XY chromosomes
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What examiners said

Several sources of genetic variation in populations were stated. Vague responses such as sexual reproduction were not credited.
— Examiner report, May/June 2025, 0970/41 Q3(c) (Cambridge)

The roles of mitosis were generally described more successfully than the actual process. Few candidates referred to the separation of chromosomes or nuclear division.
— Examiner report, May/June 2025, 0970/41 Q3(d) (Cambridge)

There was some confusion evident amongst candidates. Some tried to give two groups for each line. A small number of candidates mistakenly reversed the answers, giving sharks as the most similar and birds as the least similar.
— Examiner report, May/June 2025, 0970/41 Q5(a)(iii) (Cambridge)

Practise this topic

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In the syllabus

17.1 Chromosomes, genes and proteins

State that chromosomes are made of DNA, which contains genetic information in the form of genes
Define a gene as a length of DNA that codes for a protein
Define an allele as an alternative form of a gene
Describe the inheritance of sex in humans with reference to X and Y chromosomes
State that the sequence of bases in a gene determines the sequence of amino acids used to make a specific protein (knowledge of the details of nucleotide structure is not required)
Explain that different sequences of amino acids give different shapes to protein molecules continued
Explain that DNA controls cell function by controlling the production of proteins, including enzymes, membrane carriers and receptors for neurotransmitters
Explain how a protein is made, limited to: • the gene coding for the protein remains in the nucleus • messenger RNA (mRNA) is a copy of a gene • mRNA molecules are made in the nucleus and move to the cytoplasm • the mRNA passes through ribosomes • the ribosome assembles amino acids into protein molecules • the specific sequence of amino acids is determined by the sequence of bases in the mRNA (knowledge of the details of transcription or translation is not required)
Explain that most body cells in an organism contain the same genes, but many genes in a particular cell are not expressed because the cell only makes the specific proteins it needs
Describe a haploid nucleus as a nucleus containing a single set of chromosomes
Describe a diploid nucleus as a nucleus containing two sets of chromosomes
State that in a diploid cell, there is a pair of each type of chromosome and in a human diploid cell there are 23 pairs

17.2 Mitosis

Describe mitosis as nuclear division giving rise to genetically identical cells (details of the stages of mitosis are not required)
State the role of mitosis in growth, repair of damaged tissues, replacement of cells and asexual reproduction
State that the exact replication of chromosomes occurs before mitosis
State that during mitosis, the copies of chromosomes separate, maintaining the chromosome number in each daughter cell
Describe stem cells as unspecialised cells that divide by mitosis to produce daughter cells that can become specialised for specific functions

17.3 Meiosis

State that meiosis is involved in the production of gametes
Describe meiosis as a reduction division in which the chromosome number is halved from diploid to haploid resulting in genetically different cells (details of the stages of meiosis are not required)

17.4 Monohybrid inheritance

Describe inheritance as the transmission of genetic information from generation to generation
Describe genotype as the genetic make-up of an organism and in terms of the alleles present
Describe phenotype as the observable features of an organism
Describe homozygous as having two identical alleles of a particular gene
State that two identical homozygous individuals that breed together will be pure-breeding
Describe heterozygous as having two different alleles of a particular gene
State that a heterozygous individual will not be pure-breeding
Describe a dominant allele as an allele that is expressed if it is present in the genotype
Describe a recessive allele as an allele that is only expressed when there is no dominant allele of the gene present in the genotype
Interpret pedigree diagrams for the inheritance of a given characteristic
Use genetic diagrams to predict the results of monohybrid crosses and calculate phenotypic ratios, limited to 1 : 1 and 3 : 1 ratios
Use Punnett squares in crosses which result in more than one genotype to work out and show the possible different genotypes

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