Patterns of Inheritance | OCR A-Level Biology A (H420)
Patterns of Inheritance
- 89 questions
- 7 subtopics
- Module 6: Genetics, evolution and ecosystems
- Component 02 and Component 03
Patterns of inheritance is the second section of Module 6.
It covers what makes a phenotype vary, monogenic and dihybrid crosses and the patterns that depart from them, the chi-squared test, the forms of selection and the drift acting on small populations, the Hardy-Weinberg equations, speciation, and artificial selection.
Sample questions from Patterns of Inheritance
Answer each one closed book first, then open the answer.
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Genetic and environmental variation
How can diet affect phenotypic variation in animals?
Show the answer
Nutrient availability influences growth, body mass, coat condition, and other physical characteristics. -
Genetic and environmental variation
Why does polygenic inheritance produce continuous variation?
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Each gene adds a small effect to the phenotype, so the many possible combinations of alleles give a wide range of intermediate values, which environmental effects blur further into a continuous range. -
Monogenic and dihybrid inheritance, sex linkage and epistasis
Define codominance.
Show the answer
Codominance occurs when both alleles are expressed equally in the phenotype of a heterozygote. -
Monogenic and dihybrid inheritance, sex linkage and epistasis
Which blood groups can the children of parents with genotypes IᴬIᴼ and IᴮIᴼ have, and in what ratio?
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AB (IᴬIᴮ), A (IᴬIᴼ), B (IᴮIᴼ) and O (IᴼIᴼ), in a ratio of 1:1:1:1. -
The chi-squared test
How are degrees of freedom calculated for a chi-squared test?
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Degrees of freedom equals the number of categories minus one. -
The chi-squared test
Which level of significance is conventionally used in biology?
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The 0.05 level, meaning a probability of 5 per cent or less that the difference arose by chance. -
Selection, genetic drift and the founder effect
What effect does stabilising selection have on phenotypic variation?
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It reduces variation by selecting against extreme phenotypes. -
Selection, genetic drift and the founder effect
In which type of population does genetic drift have the greatest effect?
Show the answer
Small populations.
The 7 subtopics
One subtopic is one session. Work down the list.
| Subtopic | What it covers | Questions |
|---|---|---|
| Genetic and environmental variation | The genetic and environmental factors behind a phenotype, etiolation as a worked example, and the meiosis and random fertilisation that generate variation. | 14 |
| Monogenic and dihybrid inheritance, sex linkage and epistasis | Monogenic and dihybrid crosses and the expected ratios, multiple alleles, codominance and sex linkage, and the modified ratios that reveal linkage and epistasis. | 23 |
| The chi-squared test | What the test is for, the formula and what each term means, how degrees of freedom are found, and when the null hypothesis is rejected. | 10 |
| Selection, genetic drift and the founder effect | Stabilising and directional selection and what each does to variation, and the drift, bottlenecks and founder effects that act on small populations. | 10 |
| The Hardy-Weinberg principle | The allele and genotype frequency equations and what each term represents, and the order in which q, then p, then the genotype frequencies are calculated. | 9 |
| Speciation and isolating mechanisms | Allopatric and sympatric speciation, and the temporal, behavioural, mechanical and gametic isolation that keeps populations from interbreeding. | 10 |
| Artificial selection | What is selected for in crops and in livestock, how the selective pressure differs from natural selection, and the loss of diversity and welfare problems that can follow. | 13 |
How the guide is worked
Answering a question from memory stores it far better than reading the answer again. The guide runs that as a fixed procedure on one subtopic at a time, about twenty minutes a session.
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Step 1 · Closed book
Cover the answers. Work through one subtopic and write down what you can. Leave blanks where you have nothing.
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Step 2 · Open book
Go back to the top. Read each printed answer and write it out in full, including the ones you had right.
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Step 3 · Closed book again
Same questions, same order, from memory. The gap between pass one and pass three is the session result.
Read the full method, the return schedule and the research behind it.
Nearby sections
OCR A-Level Biology A Active Recall Guide
Every section, not just this one. 1,833 questions with their answers.