Pearson Edexcel International GCSE in Biology · 4BI1 · Free · no account needed
Monohybrid Inheritance and Probability — exam questions
11 original Incandio exam-style questions on Monohybrid Inheritance and Probability, 26 marks, about 27 minutes of writing. Each one carries the command word, the tariff and the specification statement it assesses, exactly as a paper presents them. This is an original Incandio practice question, written to reflect the structure and demands of the qualification. It is not an official Pearson Edexcel past-paper question.
This is the practice set for Monohybrid Inheritance and Probability — the lesson that teaches it. Read the lesson first if the idea is new; come here when you want to find out whether you can turn it into marks. Completely free, no account needed to read.
What these questions ask of you
9 command words run through this set, and on Pearson Edexcel International GCSE Biology each one means something precise. Answering the wrong command is the commonest way a candidate who understands the lesson still loses the mark.
- State what is meant by (1–2 marks)
- the definition
- Which (1 mark)
- one option chosen from the set given
- Explain (2–4 marks)
- a causal chain — WHY it happens, each link a separate marking point Misread as: describing what happens without giving the reason it happens
- Calculate (1–3 marks)
- a numerical answer, with working where the tariff implies steps
- Give (1–2 marks)
- a short factual answer drawn from recall or from the data
- Complete (1–5 marks)
- the missing entries in a table, diagram or sentence
- Describe (2–4 marks)
- developed, linked statements of WHAT happens — no reason required, but detail is Misread as: giving one bare statement where the tariff asked for a developed account
- Suggest (1–3 marks)
- a plausible answer applying taught biology to a situation not taught
- Use (2–5 marks)
- the supplied data, graph or diagram applied to reach a result — the data is not optional
Assessed on Paper 1 (4BI1/1B) and Paper 2 (4BI1/2B), against AO1, AO2, AO3.
Where these sit in the specification
Pearson Edexcel International GCSE Biology (4BI1) — statements 3.23 · 3.22 · 3.25. Incandio is aligned to this specification; it is not published by, endorsed by or affiliated with Pearson, and it reproduces none of Pearson's wording.
The 11 questions
Answer them on paper, then open the lesson's exam practice to have them marked. The mark scheme, the accepted and rejected answers and the annotated model answer are in Incandio and are not printed here — an answer beside its question is not practice.
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In one breed of rabbit, coat colour is controlled by a single gene. The allele for black coat (B) is dominant to the allele for brown coat (b). A breeder crosses a black rabbit that is heterozygous with a brown rabbit.
(a)
(1)Give
Give the genotype of the brown rabbit.
In one breed of rabbit, coat colour is controlled by a single gene. The allele for black coat (B) is dominant to the allele for brown coat (b). A breeder crosses a black rabbit that is heterozygous with a brown rabbit.
(b)
(3)Complete
Complete a genetic diagram for this cross, showing the parents' genotypes, their gametes and the genotypes of the offspring.
In one breed of rabbit, coat colour is controlled by a single gene. The allele for black coat (B) is dominant to the allele for brown coat (b). A breeder crosses a black rabbit that is heterozygous with a brown rabbit.
(c)
(1)Give
Give the probability that any one offspring of this cross will be brown.
In one breed of rabbit, coat colour is controlled by a single gene. The allele for black coat (B) is dominant to the allele for brown coat (b). A breeder crosses a black rabbit that is heterozygous with a brown rabbit.
(Total for Question 1 = 5 marks)
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(1)State what is meant by
State what is meant by a heterozygous organism.
(Total for Question 2 = 1 mark)
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(1)Which
Which of these human features is an example of polygenic inheritance?
Feature A blood group B height C the ability to roll the tongue D sex (Total for Question 3 = 1 mark)
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(3)Explain
Two black rabbits are bred together and one of their offspring is brown. Explain how this is possible.
(Total for Question 4 = 3 marks)
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(2)Calculate
Two heterozygous black rabbits are crossed and produce 32 offspring. Calculate how many of the offspring would be expected to be brown.
(Total for Question 5 = 2 marks)
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(3)Explain
A breeder crosses two heterozygous black rabbits and gets a litter of six, all of them black. Explain why this does not mean the expected ratio is wrong.
(Total for Question 6 = 3 marks)
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(3)Describe
Describe the difference between a feature controlled by a single gene and one that is polygenic, using an example of each.
(Total for Question 7 = 3 marks)
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(3)Suggest
A breeder wants to know whether one of her black rabbits is homozygous or heterozygous. Suggest a cross she could carry out, and how the offspring would tell her the answer.
(Total for Question 8 = 3 marks)
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(5)Use
In mice, black fur (B) is dominant to brown fur (b). Use a genetic diagram to work out the expected ratio of black to brown offspring when two heterozygous black mice are crossed, and explain why an actual litter of eight might contain no brown mice at all.
(Total for Question 9 = 5 marks)
Have them marked, then defend the answer
Practice tells you the mark; teaching it back tells you whether you understand it. On Incandio a topic counts as mastered only once you have taught it and defended it.
- Mark these questions — 11 questions, marked on Incandio against the authored scheme, with the mistake you actually made named.
- Teach it — explain Monohybrid Inheritance and Probability to Ember, an AI pupil who does not have it yet and asks the awkward question.
- Defend it — argue it against Gregor Mendel over three rounds, marked against descriptors you can read first.
Completely free. No subscriptions, no paywalls, no account needed to start.
Back to the lesson
- Monohybrid Inheritance and Probability — A method for predicting offspring, the ratio it produces — and two honest limits on what that ratio actually tells you.
- All of Incandio Biology · Incandio Exam Practice