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AP Biology · Unit 5 Practice

AP Biology Unit 5 Practice Questions: Heredity MCQ & FRQ

Practice AP Biology Unit 5 Heredity with diagnostic MCQs, full practice questions, FRQ prompts, and weak-topic review links. Start with the quick diagnostic, then move into the full practice set.

AP Biology Unit 5 practice questions cover meiosis, crossing over, independent assortment, Mendelian genetics, Punnett squares, non-Mendelian inheritance, and chi-square analysis.

Updated June 3, 2026Reviewed by APScore5 Editorial Team

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Answer 5 quick questions. Each missed question routes you to the correct Unit 5 concept page.

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Try 20 AP-style questions across Unit 5 Heredity. Each question includes an explanation and a weak-topic review link.

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Five harder Unit 5 questions on nondisjunction, linkage, non-Mendelian patterns, chi-square conclusions, and dihybrid ratios.

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AP Biology Unit 5 FRQ Practice

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Prompt

A student claims that meiosis creates genetic variation only because gametes are haploid. Explain why this claim is incomplete.

Prompt

In a monohybrid cross, two heterozygous parents are crossed. Predict the genotype and phenotype ratios under complete dominance, and explain why the ratios are probabilities.

Prompt

A student expects a 3:1 phenotype ratio in 80 offspring. The observed offspring are 58 dominant and 22 recessive. Explain how the student should use chi-square to evaluate whether the data fit the expected ratio.

Reference

All Unit 5 Practice Questions with Answers

Expand any row to review stems, choices, explanations, and study links without restarting the interactive quiz.

Diagnostic questions (5)

Diagnostic Q1 — Meiosis

Question: Which result best describes meiosis?

Choices: A) Two identical diploid body cells · B) Four genetically different haploid gametes ✓ · C) One copied chromosome · D) Two identical gametes

Correct: B. Explanation: Meiosis produces four genetically different haploid gametes. Mitosis produces two identical body cells.

Review Meiosis →

Diagnostic Q2 — Crossing Over / Independent Assortment

Question: Which process exchanges DNA between homologous chromosomes during prophase I?

Choices: A) Independent assortment · B) Crossing over ✓ · C) Cytokinesis · D) Fertilization

Correct: B. Explanation: Crossing over exchanges DNA between homologous chromosomes during prophase I and creates recombinant chromosomes.

Review Crossing Over →

Diagnostic Q3 — Punnett Squares

Question: A heterozygous monohybrid cross Aa × Aa usually produces which genotype ratio?

Choices: A) 3:1 · B) 1:1 · C) 1:2:1 ✓ · D) 9:3:3:1

Correct: C. Explanation: Aa × Aa produces 1 AA : 2 Aa : 1 aa. The phenotype ratio is 3:1 under complete dominance.

Review Punnett Squares →

Diagnostic Q4 — Non-Mendelian Genetics

Question: A red flower crossed with a white flower produces pink offspring. Which pattern is most likely?

Choices: A) Complete dominance · B) Incomplete dominance ✓ · C) Independent assortment · D) Chi-square inheritance

Correct: B. Explanation: Incomplete dominance produces an intermediate heterozygote phenotype, such as pink from red and white.

Review Non-Mendelian Genetics →

Diagnostic Q5 — Chi-Square Test

Question: What does a chi-square test compare in genetics?

Choices: A) DNA and RNA sequences · B) Observed and expected counts ✓ · C) Gametes and chromosomes only · D) Dominant and recessive alleles only

Correct: B. Explanation: A chi-square test compares observed counts with expected counts to decide whether differences are likely due to chance.

Review Chi-Square Test Genetics →

Full practice MCQs (20)

Practice Q1 — Meiosis

Question: During meiosis I, which structures separate?

Choices: A) Sister chromatids · B) Homologous chromosomes ✓ · C) Nucleotides · D) Ribosomes

Correct: B. Explanation: Meiosis I separates homologous chromosomes. Meiosis II separates sister chromatids.

Review Meiosis →

Practice Q2 — Meiosis

Question: Which phrase best describes haploid cells?

Choices: A) Cells with two sets of chromosomes · B) Cells with one set of chromosomes ✓ · C) Cells with no DNA · D) Cells produced only by mitosis

Correct: B. Explanation: Haploid cells have one set of chromosomes. Gametes are haploid.

Review Meiosis →

Practice Q3 — Meiosis

Question: Which event restores the diploid chromosome number after meiosis?

Choices: A) Crossing over · B) Fertilization ✓ · C) Independent assortment · D) Cytokinesis

Correct: B. Explanation: Meiosis creates haploid gametes. Fertilization fuses two gametes and restores diploid chromosome number.

Review Meiosis →

Practice Q4 — Crossing Over

Question: Why does crossing over increase genetic variation?

Choices: A) It creates new chromosomes from scratch. · B) It exchanges DNA between homologous chromosomes. ✓ · C) It prevents fertilization. · D) It removes all recessive alleles.

Correct: B. Explanation: Crossing over reshuffles existing alleles by exchanging DNA segments between homologous chromosomes.

Review Crossing Over →

Practice Q5 — Crossing Over

Question: A chromosome contains a new combination of maternal and paternal DNA after meiosis. What caused this?

Choices: A) Binary fission · B) Crossing over ✓ · C) Translation · D) Active transport

Correct: B. Explanation: Crossing over can produce recombinant chromosomes with new combinations of alleles.

Review Crossing Over →

Practice Q6 — Independent Assortment

Question: Independent assortment occurs because homologous chromosome pairs:

Choices: A) Line up randomly during meiosis I ✓ · B) Do not contain DNA · C) Always move together · D) Duplicate after fertilization

Correct: A. Explanation: Independent assortment comes from the random orientation of homologous chromosome pairs during meiosis I.

Review Independent Assortment →

Practice Q7 — Independent Assortment

Question: Independent assortment best explains:

Choices: A) Why linked genes always separate · B) How different chromosome combinations enter gametes ✓ · C) How proteins are made · D) Why mitosis creates identical cells

Correct: B. Explanation: Independent assortment creates different combinations of maternal and paternal chromosomes in gametes.

Review Independent Assortment →

Practice Q8 — Mitosis vs Meiosis

Question: Which statement correctly compares mitosis and meiosis?

Choices: A) Mitosis produces gametes; meiosis produces body cells. · B) Mitosis produces two identical cells; meiosis produces four different gametes. ✓ · C) Both produce four haploid cells. · D) Both reduce chromosome number.

Correct: B. Explanation: Mitosis produces two genetically identical body cells. Meiosis produces four genetically different haploid gametes.

Review Mitosis vs Meiosis →

Practice Q9 — Mitosis vs Meiosis

Question: Which clue most strongly indicates meiosis?

Choices: A) Growth and repair · B) Identical daughter cells · C) Haploid gametes ✓ · D) Replacement of skin cells

Correct: C. Explanation: Haploid gametes are produced by meiosis.

Review Mitosis vs Meiosis →

Practice Q10 — Mendelian Genetics

Question: What is a genotype?

Choices: A) Observable trait · B) Allele combination ✓ · C) Type of gamete only · D) Environmental condition

Correct: B. Explanation: A genotype is an allele combination, such as AA, Aa, or aa.

Review Mendelian Genetics →

Practice Q11 — Mendelian Genetics

Question: Which genotype is heterozygous?

Choices: A) AA · B) aa · C) Aa ✓ · D) A

Correct: C. Explanation: Heterozygous means two different alleles, such as Aa.

Review Mendelian Genetics →

Practice Q12 — Mendelian Genetics

Question: The law of segregation states that:

Choices: A) Allele pairs separate during gamete formation ✓ · B) All genes are inherited together · C) Proteins separate during translation · D) Offspring always show dominant traits

Correct: A. Explanation: The law of segregation says allele pairs separate into different gametes.

Review Mendelian Genetics →

Practice Q13 — Punnett Squares

Question: A Punnett square shows:

Choices: A) Guaranteed offspring outcomes · B) Possible genotype and phenotype probabilities ✓ · C) Protein folding patterns · D) Exact mutation rates

Correct: B. Explanation: Punnett squares show probabilities, not guaranteed offspring counts.

Review Punnett Squares →

Practice Q14 — Punnett Squares

Question: In complete dominance, Aa × Aa produces which phenotype ratio?

Choices: A) 1:2:1 · B) 3:1 ✓ · C) 1:1 · D) 9:3:3:1

Correct: B. Explanation: Aa × Aa produces a 3 dominant : 1 recessive phenotype ratio under complete dominance.

Review Punnett Squares →

Practice Q15 — Punnett Squares

Question: A test cross usually uses an unknown genotype crossed with:

Choices: A) Homozygous dominant · B) Homozygous recessive ✓ · C) Another unknown genotype · D) A haploid chromosome

Correct: B. Explanation: A test cross uses a homozygous recessive individual to reveal an unknown genotype.

Review Punnett Squares →

Practice Q16 — Non-Mendelian Genetics

Question: Which pattern shows both alleles fully expressed in the heterozygote?

Choices: A) Incomplete dominance · B) Codominance ✓ · C) Complete dominance · D) Independent assortment

Correct: B. Explanation: Codominance means both alleles are expressed, such as IA and IB in AB blood type.

Review Non-Mendelian Genetics →

Practice Q17 — Non-Mendelian Genetics

Question: ABO blood type is an example of:

Choices: A) Multiple alleles and codominance ✓ · B) Mitosis only · C) Crossing over only · D) Complete dominance only

Correct: A. Explanation: ABO blood type uses multiple alleles, and IA and IB are codominant.

Review Non-Mendelian Genetics →

Practice Q18 — Non-Mendelian Genetics

Question: A trait controlled by many genes and showing continuous variation is:

Choices: A) Polygenic ✓ · B) Haploid · C) Codon-based · D) Identical

Correct: A. Explanation: Polygenic traits are influenced by multiple genes and often show continuous variation.

Review Non-Mendelian Genetics →

Practice Q19 — Chi-Square

Question: A chi-square test should use:

Choices: A) Percentages only · B) Observed and expected counts ✓ · C) DNA base-pair rules · D) Protein sequences only

Correct: B. Explanation: Chi-square uses observed and expected counts for each category.

Review Chi-Square →

Practice Q20 — Chi-Square Data

Question: Using a 3:1 phenotype ratio in 80 offspring (observed: 58 dominant, 22 recessive), what is the expected count for the recessive phenotype?

PhenotypeObservedExpected (3:1)
Dominant5860
Recessive2220

Choices: A) 15 · B) 20 ✓ · C) 22 · D) 58

Correct: B. Explanation: For a 3:1 ratio in 80 offspring, expected recessive count is 80 ÷ 4 = 20. Observed 22 is close to expected, so a chi-square test would likely fail to reject the null hypothesis.

Review Chi-Square →

Challenge MCQs (5)

Challenge Q1 — Meiosis / Nondisjunction

Question: Nondisjunction during meiosis I most often produces gametes with:

Choices: A) Normal chromosome number only · B) An abnormal chromosome number ✓ · C) No DNA · D) Identical diploid body cells

Correct: B. Explanation: Nondisjunction is failure of chromosomes to separate, producing n±1 gametes and offspring with abnormal chromosome number.

Review Meiosis →

Challenge Q2 — Linkage

Question: Genes on the same chromosome that tend to be inherited together show:

Choices: A) Independent assortment · B) Linkage ✓ · C) Codominance only · D) Haploid division

Correct: B. Explanation: Linked genes on one chromosome are inherited together unless crossing over separates them. Independent assortment applies to genes on different chromosomes.

Review Independent Assortment →

Challenge Q3 — Non-Mendelian Genetics

Question: A red × white cross produces pink offspring. A pink × pink cross yields 1 red : 2 pink : 1 white. Which pattern best fits the data?

Choices: A) Codominance · B) Incomplete dominance ✓ · C) Linkage · D) Polygenic inheritance

Correct: B. Explanation: A blended heterozygote and 1:2:1 offspring ratio indicate incomplete dominance, not codominance where both alleles are fully expressed.

Review Non-Mendelian Genetics →

Challenge Q4 — Chi-Square Conclusion

Question: A student calculates χ² = 2.1 with df = 1. The critical value at α = 0.05 is 3.84. The best conclusion is:

Choices: A) Reject the null hypothesis · B) Fail to reject the null hypothesis ✓ · C) The test is invalid · D) Always accept the null when χ² > 0

Correct: B. Explanation: Because 2.1 is less than the critical value 3.84, fail to reject the null hypothesis. The observed counts are not significantly different from expected at α = 0.05.

Review Chi-Square →

Challenge Q5 — Dihybrid Ratio & df

Question: A dihybrid cross with independent assortment and complete dominance expects which phenotype ratio, and what is df for a chi-square test?

Choices: A) 9:3:3:1 ratio; df = 3 ✓ · B) 3:1 ratio; df = 1 · C) 1:2:1 ratio; df = 2 · D) 9:3:3:1 ratio; df = 4

Correct: A. Explanation: Four phenotype categories in a 9:3:3:1 ratio give df = categories − 1 = 3.

Review Chi-Square →

FRQ prompts (3)

FRQ 1 — Meiosis and Genetic Variation

Prompt: A student claims that meiosis creates genetic variation only because gametes are haploid. Explain why this claim is incomplete.

Sample answer: The claim is incomplete because haploid gametes explain chromosome number, not all genetic variation. Meiosis creates variation through crossing over, which exchanges DNA between homologous chromosomes, and independent assortment, which randomly sorts homologous chromosome pairs into gametes. Random fertilization also increases variation because any sperm can combine with any egg.

FRQ 2 — Punnett Square Reasoning

Prompt: In a monohybrid cross, two heterozygous parents are crossed. Predict the genotype and phenotype ratios under complete dominance, and explain why the ratios are probabilities.

Sample answer: For Aa × Aa, each parent can produce A or a gametes. The offspring genotypes are AA, Aa, Aa, and aa, giving a 1:2:1 genotype ratio. Under complete dominance, AA and Aa show the dominant phenotype, so the phenotype ratio is 3:1. These ratios are probabilities because fertilization is random.

FRQ 3 — Chi-Square Interpretation

Prompt: A student expects a 3:1 phenotype ratio in 80 offspring. The observed offspring are 58 dominant and 22 recessive. Explain how the student should use chi-square to evaluate whether the data fit the expected ratio.

Sample answer: For 80 offspring in a 3:1 ratio, the expected counts are 60 dominant and 20 recessive. The chi-square test compares these expected counts with the observed counts of 58 and 22. Because the differences are small, the calculated chi-square value would likely be low. The student should compare the calculated value to the critical value using the correct degrees of freedom. If the calculated value is below the critical value, the student should fail to reject the null hypothesis.

Benchmarks

Score Yourself

ScoreMeaningNext step
Diagnostic (out of 5)
0–2Review firstStudy weak-topic guides, then retake diagnostic
3–4DevelopingStart full 20-question practice
5Strong foundationRun full practice and FRQs
Full MCQ (out of 20)
0–8Needs reviewReturn to missed topic pages
9–13DevelopingMix review + retake
14–17StrongAdd FRQ practice
18–20ExcellentKeep FRQs sharp before the exam
FRQ (3 prompts)
0 attemptedNot startedTry at least one FRQ
1 attemptedGood startCompare draft to rubric
2 attemptedStrong practiceFinish the third FRQ
3 attemptedUnit 5 FRQ readyReview Unit 5 hub
Confidence

What You Can Now Do

0 of 6 ready

Quick answers

Frequently Asked Questions

What is on AP Biology Unit 5?

AP Biology Unit 5 is Heredity. It covers meiosis, crossing over, independent assortment, Mendelian genetics, Punnett squares, non-Mendelian inheritance, and chi-square analysis. The AP exam mixes MCQs with data-based FRQs in this unit.

How many AP Biology Unit 5 practice questions should I do?

Start with the 5-question diagnostic, then complete the 20 MCQs and at least one FRQ. Review every missed question before adding more sets from other sources.

What topics are tested in AP Biology Unit 5 Heredity?

Meiosis, mitosis vs meiosis, crossing over, independent assortment, Mendelian genetics, Punnett squares, non-Mendelian patterns, and chi-square tests appear often on Unit 5 items.

Are Punnett squares important for AP Biology Unit 5?

Yes. Punnett squares model probability for genotype and phenotype ratios. They pair with Mendelian and non-Mendelian patterns on both MCQs and FRQs.

Does AP Biology Unit 5 include chi-square?

Yes. Chi-square compares observed offspring counts to expected counts from an inheritance model. You must interpret the conclusion, not only compute the statistic.

How should I study for AP Biology Unit 5 MCQs?

Take the diagnostic, review weak-topic guides linked from wrong answers, then run the full 20-question practice. Explain why each answer is correct in your own words.

How should I answer AP Biology Unit 5 FRQs?

State a clear claim, cite data or ratios, connect to chromosomes or alleles, and end with a biological conclusion. Use vocabulary from the prompt.

What score means I am ready for Unit 5?

A strong signal is 4–5 on the diagnostic, 14+ on the full MCQ set, and drafts on all three FRQs with rubric-aligned reasoning.

Should I memorize ratios or understand them?

Understand them. The exam changes cross types and inheritance patterns. If you can derive a ratio from gametes, you are safer than memorizing 3:1 alone.

Where should I go if I miss questions?

Use the review link under each explanation. Return to the matching Unit 5 guide—meiosis, Punnett squares, non-Mendelian genetics, or chi-square—before retaking the quiz.

← Review weak topicMeiosis ↻Retake diagnostic Unit 5Unit 5 hub
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