AP Bio · Unit 5 Progress Check

AP Biology Unit 5 Progress Check: Heredity MCQ and FRQ walkthrough

AP Biology Unit 5 is heredity: meiosis, Mendelian and non-Mendelian crosses, pedigrees, and the chi-square test. College Board publishes what the Unit 5 Progress Check contains, about 23 multiple-choice questions and two free-response questions, and this walkthrough covers what each one tests and where the points sit. Explanations only; we never publish AP Classroom answer keys. Every unit is on the AP Biology Progress Check answers hub.

Updated September 2026Written by Mahmudul HasanFree · No signup

What AP Biology Unit 5 covers

College Board weights Unit 5 at 8–11% of the AP Biology multiple-choice section. The scope matters: the unit weightings in the Course and Exam Description cover the multiple-choice section only, and College Board publishes no unit weighting for the free-response section at all. Within the course, 8–11% ties Unit 1 for the joint-lowest weighting, and at about 8 to 10 class periods Unit 5 is also the shortest unit, against roughly 19 to 21 periods for Natural Selection and Ecology.

College Board splits the unit into five numbered topics, and those are the labels you will see in AP Classroom.

5.1 Meiosis

How a diploid cell produces haploid gametes. Meiosis I separates homologous chromosomes; meiosis II separates sister chromatids. Knowing which division does which is what the error questions turn on.

5.2 Meiosis and Genetic Diversity

Crossing over in prophase I, independent assortment, and random fertilization. This topic is also where nondisjunction lives: incorrect separation leaves a gamete that is no longer haploid.

5.3 Mendelian Genetics

Segregation and independent assortment, monohybrid and dihybrid crosses, Punnett squares, and reading pedigrees to work out whether an allele is dominant or recessive.

5.4 Non-Mendelian Genetics

Incomplete dominance, codominance, multiple alleles, polygenic and sex-linked traits, pleiotropy, linked genes and recombination frequency, and non-nuclear inheritance through mitochondrial and chloroplast DNA, which is typically maternally inherited.

5.5 Environmental Effects on Phenotype

The same genotype giving different phenotypes under different conditions, which is why identical genes do not guarantee identical organisms.

Chi-square, across 5.3 and 5.4

Not a topic of its own. College Board pairs the skill “perform chi-square hypothesis testing” with both Mendelian and non-Mendelian genetics, which is why the test shows up throughout the unit.

The Unit 5 Progress Check MCQ: what each question type tests

The Unit 5 Progress Check runs about 23 multiple-choice questions alongside its two free-response questions. College Board publishes something more useful than the count, though: the specific skill it pairs with each topic. Meiosis is paired with explaining a biological process, genetic diversity with posing a testable question, Mendelian genetics with chi-square testing and with predicting the effect of a change on a system, non-Mendelian genetics with calculation and with chi-square again, and environmental effects with explaining a concept in an applied context.

That pairing is worth knowing because of what College Board says next about it: the Progress Check questions are built on it, while exam questions can pair the same content with any of the skills. A Progress Check is a check on one unit against one designated skill, which is a different thing from a rehearsal for the exam.

Cross prediction

Almost every lost point here comes from writing down the wrong parental genotypes. Decide whether each parent is homozygous dominant, heterozygous or homozygous recessive before you draw anything, and use a test cross when the question gives you an unknown dominant. For a dihybrid, multiplying the two single-trait probabilities is faster than a sixteen-box grid, and the laws of probability are on the reference sheet.

Pedigree inference

Two unaffected parents with an affected child means the trait is recessive, because both parents must be carriers. Then check the sexes: if affected individuals are overwhelmingly male, look at X-linked recessive. Autosomal and sex-linked patterns can look identical in a small family, so the question usually gives you enough generations to separate them.

Chi-square reasoning

These are usually conceptual rather than computational. You are asked whether the statistic clears the critical value at the right degrees of freedom, and what that means for the null hypothesis. Read whether the question wants the decision or the interpretation before you start arithmetic.

Non-Mendelian recognition

A 1:2:1 phenotype ratio signals incomplete dominance or codominance, not simple dominance, because the heterozygote shows its own phenotype instead of hiding behind the dominant allele. Traits that follow the maternal line regardless of the father point at mitochondrial or chloroplast DNA rather than at anything on a chromosome.

Meiosis errors

Nondisjunction questions ask which division produced an abnormal gamete, and the answer is in what failed to separate. A gamete carrying both homologues of a pair points at meiosis I; one carrying both sister chromatids of a single chromosome points at meiosis II.

The Unit 5 Progress Check FRQ: the two questions College Board names

College Board names both of them. The Unit 5 Progress Check carries two free-response questions: Interpreting and Evaluating Experimental Results with Graphing, and Conceptual Analysis. Three of the eight AP Biology Progress Checks hand out shortened partial versions of their free-response questions. Unit 5 is not one of them, so both of these are the full-length forms that College Board says exist to prepare students for the complete questions on the exam.

On the exam itself, Interpreting and Evaluating Experimental Results with Graphing is question 2, and it is worth 9 points split four ways.

The nine points on the exam-length version of this question type, as College Board splits them. A, describe a biological concept, process or model: 1 point. B, construct the appropriate graph from the data provided: 4 points. C, analyze data, perform calculations, state a null hypothesis or predict results: 2 points. D, make and justify predictions: 2 points. Source: AP Biology Course and Exam Description, printed p. 201.

That split is the thing to take away, and it is not what most students expect on the unit everyone calls the chi-square unit. The graph is worth more than the statistics. Choosing the right type of graph, labeling the axes with units, scaling them sensibly and plotting the points accurately carry four of the nine points between them. The chi-square work sits in part C, sharing two points with data analysis and prediction.

When chi-square does come up, the chain is: state the null hypothesis, calculate the expected values from the ratio you predicted, compute the statistic, compare it against the critical value at the correct degrees of freedom, and say what that means biologically. You are not asked to memorize any of the numbers. The formula and the critical values for 1 to 8 degrees of freedom are printed in College Board’s reference information for AP Biology, which is mailed to schools and available in Bluebook in the test preview and on exam day, and the laws of probability are on the same sheet. The AP Biology formula sheet page covers what else is on it.

The second question, Conceptual Analysis, is the short-answer type; on the exam the four short questions are worth 4 points each. It asks you to explain a heredity concept rather than to compute with it, which is why revising Unit 5 only through Punnett-square arithmetic leaves half of the Progress Check unprepared.

Where the AP Classroom Unit 5 Progress Check MCQ answers actually are

If you are looking for AP Bio Unit 5 answers because nobody has gone through the Progress Check with you, there is a legitimate place to look, and it is the platform you already have. College Board states that Progress Check multiple-choice questions come with rationales explaining both the correct and the incorrect answers, and that the free-response questions come with scoring information. Those sit inside AP Classroom, and your teacher controls when they are released.

So the route is: finish the Progress Check, ask your teacher to release the results, then read the rationale on every question you missed and on at least one you guessed right. That is a better artifact than an answer key, because it tells you why. If the rationales have not been released, the reasoning on this page and College Board’s own published free-response questions and scoring information are what is left, and neither of them is a shortcut.

Curve does not publish AP Classroom answer keys. No page that does is doing you a favor either: the work is graded as your own, College Board rotates the items, and a leaked key teaches you nothing about the question you get next.

Where students lose the most points on Unit 5

College Board names two of these itself in the guidance it writes for Unit 5 teachers: students state an alternate hypothesis where the null was asked for, and they confuse genotypic ratios with phenotypic ones.

Getting degrees of freedom wrong

Degrees of freedom counts phenotype categories, minus 1. A cross with four phenotypes gives df = 3, however many offspring were scored. The sample size never enters it.

Stating the alternate hypothesis instead of the null

College Board flags this as a common exam error. The null is the no-significant-difference statement: the offspring fit the predicted ratio and any deviation is chance. Anything asserting a real difference is the alternative, and it earns nothing where the null was asked for.

Confusing genotype and phenotype ratios

A cross between two heterozygotes gives a 1:2:1 genotype ratio and a 3:1 phenotype ratio. College Board names the confusion between the two as a common student error, so check which one the question asked for before you start counting boxes.

Assuming sex-linked means male-only

Females can be affected by a recessive X-linked trait; they need two copies rather than one. Males carry a single X, which is why they are affected more often, not exclusively.

Concluding “the data is wrong”

A chi-square above the critical value means the deviation is too large to write off as chance, so you reject the null. That is a result, and often the interesting one: inheritance departing from an expected ratio is what linkage and sex-linkage look like in data. Below the critical value you fail to reject, which is not the same as proving the ratio.

How to work through AP Biology Unit 5

Work the five topics in order the first time. Unit 5 is short, but 5.3 and 5.4 carry the chi-square skill and both of the calculation-heavy question types, so they are worth more of your revision than their length suggests.

Practice the graph before you practice the statistic. Four of the nine points on the exam-length version of this unit’s free-response type are for constructing the graph, and it is the part students skip when revising because it feels like presentation rather than biology.

For any chi-square question, write the null hypothesis first and the degrees of freedom second, before you touch a calculator. Those two lines take about fifteen seconds and they carry more of the rubric than the arithmetic does.

Once you have finished the Progress Check, put your raw score into our AP Biology Calculator to see roughly where that score would land on the 1–5 scale, and use the AP Biology Review for the full exam format and study plan. Treat the number as a rough gauge rather than a forecast: a Progress Check is formative, College Board attaches no 1–5 scale to it, and its questions are built on that fixed topic-to-skill pairing while the exam is free to pair the same content with any skill.

Frequently asked questions

Quick answers, checked against College Board.

How many questions is the AP Biology Unit 5 Progress Check?

College Board publishes the composition: about 23 multiple-choice questions and 2 free-response questions, named Interpreting and Evaluating Experimental Results with Graphing, and Conceptual Analysis. Unit 5 is one of the Progress Checks that gives the full-length free-response versions rather than the shortened ones.

Is the chi-square table given to you on the AP Biology exam?

Yes. The chi-square formula and the critical values for 1 to 8 degrees of freedom are printed in College Board’s reference information for AP Biology, along with the laws of probability. It is mailed to schools and available in Bluebook. The marks are in choosing the test and reading the result, not in recall.

Where can I see the answers to my Unit 5 Progress Check?

In AP Classroom. College Board says Progress Check multiple-choice questions carry rationales explaining the correct and the incorrect answers, and the free-response questions carry scoring information. Your teacher decides when to release them, so ask if they have not.

Does a Progress Check score predict my AP score?

Not reliably. Progress Checks are formative and College Board attaches no 1–5 scale to them. Its own course description says Progress Check questions are built on a fixed topic-to-skill pairing while exam questions can pair the content with any of the skills, so the exam can ask something the Progress Check never did.