WJEC A Level Biology
WJEC A Level Biology 4.3 Inheritance Exam Questions
Free WJEC A Level Biology exam questions on 4.3 Inheritance, with mark schemes. Covers monohybrid and dihybrid crosses, codominance, sex linkage, linkage and the chi-squared test.
4.3 Inheritance exam questions
1 question pack of real past exam questions with its mark scheme. Answer every question without notes, then mark your answers line by line against the mark scheme.
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WJEC A Level Biology Flashcards (Anki & Quizlet)
Every answer is written in mark scheme wording, so you learn exactly what examiners give marks for. Use them on Anki or Quizlet, then test yourself with the questions on this page.
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About WJEC A Level Biology 4.3 Inheritance
This topic covers how characteristics are inherited. Expect genetic diagrams and chi-squared calculations.
What you need to know
- Monohybrid and dihybrid crosses Genetic diagrams with expected ratios such as 3:1 and 9:3:3:1.
- Codominance and multiple alleles Both alleles expressed, such as ABO blood groups.
- Sex linkage Genes on the X chromosome, such as haemophilia, more often affect males.
- Chi-squared Testing whether observed results differ significantly from expected ratios.
Common mistakes in 4.3 Inheritance
- Not showing gametes in genetic diagrams.
- Using the wrong degrees of freedom in chi-squared.
- Forgetting males have only one X chromosome.
Try three 4.3 Inheritance exam-style questions
1. State the expected phenotype ratio from a dihybrid cross between two heterozygotes. (1 mark)
Show the mark scheme answer
9:3:3:1.
2. Explain why sex-linked disorders are more common in males. (2 marks)
Show the mark scheme answer
Males have one X chromosome (1), so a single recessive allele is expressed (1).
3. State what a chi-squared value greater than the critical value shows. (1 mark)
Show the mark scheme answer
The difference between observed and expected results is significant, not due to chance.
4.3 Inheritance FAQs
What does Inheritance cover?
Monohybrid and dihybrid inheritance, codominance, sex linkage, linkage and chi-squared.
Do I need to calculate chi-squared?
Yes, and interpret it using degrees of freedom and a critical value.
What is autosomal linkage?
Genes on the same chromosome inherited together, altering expected ratios.
Revise this topic with flashcards: WJEC A Level Biology Flashcards, with mark scheme answers for Anki and Quizlet.
