AP Courses AP Biology AP Biology Units AP Human Geography AP HUG Units AP Computer Science Principles AP CSP Units
Practice Daily Practice Practice by Course Practice by Topic Practice Tests
AP Exam Resources AP Exam Dates Registration Fees Scores & Credit What to Bring
Start Practicing → Login Register →
AP Biology · Unit 5

AP Biology Unit 5 Review: Heredity

AP Biology Unit 5 explains how traits are passed from parents to offspring through meiosis, genetic variation, Mendelian inheritance, Punnett squares, non-Mendelian patterns, sex-linked traits, and pedigrees. The big idea is simple: heredity depends on how chromosomes, alleles, and gametes move across generations.

Teacher tip: In Unit 5, always ask three questions: What alleles are present? How do they separate into gametes? What offspring genotypes and phenotypes are possible?

Updated June 4, 2026 • Reviewed by APScore5 Editorial Team

Start the Unit 5 Journey → Practice MCQs → Start Meiosis →
Unit 5 heredity AP Bio hub
Figure - Unit 5 Heredity AP Biology Hub
MeiosisGenetic variationPunnett squaresInheritance patternsPedigreesFRQ reasoning

What is AP Biology Unit 5?

AP Biology Unit 5 is about heredity: how genetic information passes from one generation to the next. Students learn how meiosis forms haploid gametes, how crossing over and independent assortment increase genetic variation, how Mendelian and non-Mendelian patterns predict traits, and how pedigrees reveal inheritance across families.

Unit 5 in one sentence

Heredity explains how chromosomes, alleles, and gametes create inheritance patterns.

Browse the full AP Biology course hub, drill weak areas with practice by topic, or jump to Unit 5 practice questions.

Learning journey

Follow the AP Bio Unit 5 Learning Journey

Each card below links to a dedicated Unit 5 guide. Follow the sequence from meiosis through variation, inheritance patterns, Punnett squares, pedigrees, and full practice sets.

MeiosisLearn how gametes form through two divisions.Study guide Mitosis vs MeiosisCompare body-cell division with gamete formation.Study guide Crossing OverSee how homologous chromosomes exchange DNA.Study guide Independent AssortmentLearn how chromosome pairs separate randomly.Study guide Genetic VariationConnect meiosis, fertilization, and mutation to variation.Study guide Mendelian GeneticsMaster alleles, dominance, genotypes, and phenotypes.Study guide Punnett SquaresPredict offspring genotype and phenotype ratios.Study guide Monohybrid CrossesTrack one trait using allele combinations.Study guide Dihybrid CrossesTrack two traits and independent assortment.Study guide Non-Mendelian InheritanceStudy traits that do not follow simple dominance.Study guide Sex-Linked TraitsExplain inheritance patterns on sex chromosomes.Study guide PedigreesRead family trees to infer inheritance patterns.Study guide AP Biology Unit 5 Practice QuestionsPractice MCQs and FRQs for heredity.Practice

Suggested study path: Suggested path: Meiosis → Crossing Over → Independent Assortment → Genetic Variation → Mendelian Genetics → Punnett Squares → Monohybrid & Dihybrid Crosses → Non-Mendelian Inheritance → Sex-Linked Traits → Pedigrees → Unit 5 Practice Questions.

Key Takeaways for AP Biology Unit 5

  • Meiosis produces haploid gametes and reduces chromosome number.
  • Crossing over and independent assortment create genetic variation.
  • Mendelian genetics predicts inheritance using alleles, genotypes, and phenotypes.
  • Punnett squares model probability, not guaranteed offspring results.
  • Pedigrees help infer inheritance patterns across generations.
Section A

Meiosis Creates Gametes

Meiosis has two divisions that produce haploid gametes. Meiosis I separates homologous chromosomes; meiosis II separates sister chromatids. This reduces chromosome number so fertilization restores the diploid state.

Meiosis variation AP Bio
Figure - Meiosis Creates Genetic Variation Guide

Deeper guides: Meiosis and Mitosis vs Meiosis. Crossing over happens in prophase I—see Crossing Over.

Meiosis connects to cell cycle control from Unit 4 and chromosome structure from Unit 2 organelles.

Section B

Genetic Variation Comes From Meiosis and Fertilization

Variation increases through crossing over, independent assortment, random fertilization, and mutation. AP questions often ask you to name which source explains a new allele combination.

Study guides: Crossing Over, Independent Assortment, and Genetic Variation.

Section C

Mendelian Genetics Predicts Simple Inheritance

Alleles are alternate forms of a gene. Dominant alleles mask recessive ones in heterozygotes. Genotype is allele combination; phenotype is the expressed trait. Homozygous means two identical alleles; heterozygous means two different alleles.

Full guide: Mendelian Genetics. DNA structure from Unit 1 nucleic acids supports why alleles are different DNA sequences.

Section D

Punnett Squares Organize Probability

Punnett squares map parental gametes to possible offspring genotypes. Monohybrid crosses track one gene; dihybrid crosses track two genes when alleles assort independently. Squares show probability, not guaranteed counts.

Inheritance patterns AP Bio
Figure - Inheritance Patterns And Punnett Outcomes

Deep dives: Punnett Squares, Monohybrid Crosses, and Dihybrid Crosses.

Section E

Non-Mendelian Inheritance Adds Complexity

Not every trait follows simple dominance. Incomplete dominance blends phenotypes. Codominance shows both alleles. Multiple alleles and polygenic traits create more phenotypes than a 3:1 ratio predicts.

Guides: Non-Mendelian Inheritance and Sex-Linked Traits.

Section F

Pedigrees Reveal Family Patterns

Pedigree charts use standard symbols to trace traits across generations. AP students infer autosomal dominant, autosomal recessive, and sex-linked patterns from who is affected and how the trait passes through carriers.

Pedigree logic AP Bio
Figure - Pedigree Symbols And Family Patterns

Full guide: Pedigrees.

AP Bio Unit 5 Exam Clues

Exam clue

If the question says “gametes,” think meiosis.

Exam clue

If the question says “homologous chromosomes exchange segments,” think crossing over.

Exam clue

If the question says “random chromosome alignment,” think independent assortment.

Exam clue

If the question asks for offspring probabilities, use Punnett squares.

Exam clue

If the question shows a family tree, use pedigree logic.

Exam clue

If observed data differs from expected ratios, explain variation or sample size—not chi-square yet.

Common Unit 5 Mistakes

Homologous chromosomes vs sister chromatids

Fix: Homologous chromosomes carry the same genes; sister chromatids are copied versions of one chromosome.

Genotype vs phenotype

Fix: Genotype is allele combination; phenotype is observable trait.

Probability vs guarantee

Fix: Punnett squares show possible outcomes, not exact offspring counts.

Mitosis vs meiosis

Fix: Mitosis maintains chromosome number; meiosis reduces it for gametes.

Dominant vs common

Fix: Dominant alleles are expressed in heterozygotes; they are not always more common in populations.

Sex-linked vs sex-influenced

Fix: For this Unit 5 hub, focus on genes located on sex chromosomes, especially X-linked inheritance.

FRQ strategy

How to Answer AP Biology Unit 5 FRQs

  1. Identify the inheritance pattern.
  2. Define the alleles or chromosome behavior.
  3. Predict gametes or offspring genotypes.
  4. Connect genotype to phenotype.
  5. Use evidence from the prompt.
  6. Explain probability carefully.

FRQ writing sentence frames

  • “Because the allele is recessive, the phenotype appears only when…”
  • “During meiosis I, homologous chromosomes…”
  • “Crossing over increases genetic variation by…”
  • “The pedigree pattern supports ___ inheritance because…”
Unit 5 FRQ reasoning AP Bio
Figure - Unit 5 FRQ Reasoning Evidence Flow
Mini practice

Try Three Unit 5 Questions

Tap an answer to check your reasoning, then open full practice sets.

Variation

Which process directly increases genetic variation by exchanging DNA between homologous chromosomes?

Punnett squares

A Punnett square predicts which outcome?

Pedigrees

A pedigree shows a trait appearing mostly in males and being passed through carrier females. Which pattern is most likely?

Start Unit 5 Practice Questions → Review Punnett Squares → Review Meiosis →

AP Biology Unit 5 FAQs

What is AP Biology Unit 5 about?

AP Biology Unit 5 is about heredity—how genetic information passes from parents to offspring. Students study meiosis, genetic variation, Mendelian and non-Mendelian inheritance, Punnett squares, sex-linked traits, and pedigrees.

Is AP Biology Unit 5 hard?

Unit 5 is moderate difficulty because it combines chromosome behavior with probability reasoning. Students who connect meiosis to gametes and explain inheritance patterns step by step usually score higher on MCQs and FRQs.

What are the most important Unit 5 topics?

Prioritize meiosis, crossing over, independent assortment, Mendelian genetics, Punnett squares, non-Mendelian inheritance, sex-linked traits, and pedigree analysis. Practice predicting gametes and offspring ratios from prompt evidence.

What is the difference between mitosis and meiosis?

Mitosis produces genetically similar body cells and maintains chromosome number. Meiosis produces haploid gametes, reduces chromosome number by half, and creates genetic variation through crossing over and independent assortment.

Why does meiosis create genetic variation?

Meiosis creates variation through crossing over (DNA exchange between homologous chromosomes), independent assortment (random alignment of homologous pairs), and the random fusion of gametes during fertilization.

What is crossing over?

Crossing over is the exchange of DNA segments between homologous chromosomes during prophase I of meiosis. It creates recombinant chromosomes with new allele combinations.

What is independent assortment?

Independent assortment is the random separation of homologous chromosome pairs during meiosis I. It increases the number of possible gamete allele combinations.

What do Punnett squares show?

Punnett squares show possible offspring genotypes and phenotype probabilities based on parental gametes. They model probability—they do not guarantee exact offspring counts.

What is the difference between genotype and phenotype?

Genotype is the allele combination an organism carries (such as Aa). Phenotype is the observable trait or expression of that genotype.

What is non-Mendelian inheritance?

Non-Mendelian inheritance includes patterns that do not follow simple dominant–recessive ratios, such as incomplete dominance, codominance, multiple alleles, and polygenic traits.

How do pedigrees work in AP Biology?

Pedigrees use standardized symbols to trace traits across generations. AP students infer whether a trait is autosomal dominant, autosomal recessive, or sex-linked from family patterns.

How should I study for AP Biology Unit 5 FRQs?

Identify the inheritance pattern, define alleles, predict gametes, connect genotype to phenotype, use prompt evidence, and explain probability as a ratio or fraction—not a guarantee.

Where can I practice AP Biology Unit 5 questions?

Start with the three mini MCQs on this page, then open the Unit 5 practice questions guide for full MCQ and FRQ sets with explanations.

Is there an AP Bio Unit 5 Quizlet or Scribd version?

Quizlet and Scribd sets exist for Unit 5 vocabulary, but this hub includes linked study guides, mini MCQs with explanations, and a full practice questions page with FRQ-style scenarios.

How do I get AP Bio Unit 5 test answers?

Real AP exam questions are secure. Use the on-page practice MCQs and the Unit 5 practice questions guide to build the same reasoning skills legally.

What's the best way to review AP Bio Units 1–5?

Review cumulatively: Unit 1 chemistry supports protein and DNA structure; Units 2–4 connect to cell division and signaling; Unit 5 ties meiosis and inheritance together. Revisit each unit hub and drill weak microtopics with practice by topic.

Keep going

Ready to master AP Biology Unit 5?

Start with meiosis, then move through genetic variation, inheritance patterns, Punnett squares, pedigrees, and practice questions.

Start Meiosis → Practice Unit 5 Questions → Back to AP Biology
Continue learning

Next: AP Biology Unit 6 Gene Expression

Heredity sets the alleles offspring inherit. Unit 6 explains how those genes are expressed through transcription, translation, and regulation.

Start Unit 6 → AP Biology course hub
Unit 5 progress0%