AP Bio · Unit 6 Progress Check

AP Biology Unit 6 Progress Check: Gene Expression and Regulation walkthrough.

College Board publishes what is on the AP Biology Unit 6 Progress Check: about 25 multiple-choice questions and two free-response questions, both full length rather than the shortened versions some units get. This page names both question types, shows where their points sit, and works through the reasoning the MCQ tests. We explain; we never publish AP Classroom answer keys.

Updated September 2026Written by Mahmudul HasanFree · No signup

Working through the whole course? Every unit is covered in all eight AP Biology Progress Check walkthroughs.

What Unit 6 covers

Unit 6 is Gene Expression and Regulation. College Board weights it at 12–16% of the multiple-choice section of the AP Exam — one of the heaviest units, level with Cellular Energetics and behind only Natural Selection. It is also long: about 18 to 20 class periods, the third-longest unit in the course and roughly double what College Board suggests for Heredity. College Board divides it into eight topics. To learn the content itself before you practice, read our AP Bio Unit 6 review.

6.1 DNA and RNA Structure

Base pairing, purines against pyrimidines, how eukaryotic chromosomes are packed around histones, and what a plasmid is.

6.2 DNA Replication

Semiconservative copying, leading and lagging strands, and the five enzymes College Board keeps in scope.

6.3 Transcription and RNA Processing

DNA to mRNA, then what eukaryotes do to the transcript: a GTP cap, a poly-A tail, and alternative splicing of introns and exons.

6.4 Translation

Codons, tRNA anticodons, the ribosome, and stopping at a stop codon to release the polypeptide.

6.5 Regulation of Gene Expression

Regulatory sequences and the proteins that bind them. Some genes run constantly; others are inducible. Prokaryotes group genes into operons run as inducible or repressible systems.

6.6 Gene Expression and Cell Specialization

Transcription factors binding promoters and enhancers, negative regulatory molecules blocking transcription, and why two cells with one genome do different jobs.

6.7 Mutations

Point, frameshift, nonsense and silent. Beneficial, detrimental or neutral, depending on the environment the organism is in.

6.8 Biotechnology

Gel electrophoresis, PCR, bacterial transformation and DNA sequencing, and what each one is actually for.

College Board also publishes what is not examinable here, and that is worth as much as the list above. On replication it names the five enzymes that stay in scope: DNA polymerase, ligase, RNA polymerase, helicase and topoisomerase. The other enzyme names and the names of the steps are out of scope. Specific named mutations and their effects are out of scope. So are specific chromosome-number disorders, and the internal details of each biotechnology technique: you need to know what gel electrophoresis does, not how to run one. All of it is set out in the AP Biology Course and Exam Description.

The Unit 6 Progress Check MCQ: what each question type tests

College Board publishes what is on it: about 25 multiple-choice questions, drawn from all eight topics in the unit. It also pairs every topic with one specific skill it wants tested there, which is what makes the question shapes below predictable. Unit 6 leans on two skills in particular, visual representations and argumentation. Across the multiple-choice section as a whole those two practices carry 16 to 24 percent and 20 to 26 percent of the questions respectively, and half of Unit 6’s topics are paired with each.

Central dogma sequencing

The question changes one step and asks what happens downstream to the protein.

Operon logic

The question sets a condition and asks what transcription does next. Inducible systems switch on; repressible systems switch off.

Mutation consequence

The question gives you a mutation and asks what it does to the protein. A frameshift shifts the reading frame from that point to the end; a substitution changes one amino acid at most, and sometimes none.

Gel electrophoresis

The question shows a gel and asks what the bands mean. Fragments separate by size and charge, and the smaller ones travel further.

Differential expression

The question compares two cell types from one organism. Same genome, different cells — the answer is always regulation, not gene loss.

Model and diagram reading

The question hands you a diagram rather than a paragraph. Half of Unit 6’s topics are paired with a visual-representation skill, which is why.

The Progress Check FRQ

College Board names both of them. Progress Check 6’s free response is Interpreting and Evaluating Experimental Results and Analyze Model or Visual Representation of a Biological Concept or Process, and those are the same two question types that appear on the exam as Question 1 and Question 5. Unit 6 gets the full-length versions, so the work is exam-length work. For the free-response section as a whole, see the AP Biology free-response guide, or College Board’s AP Biology exam page for the format.

The first is a 9-point question, and College Board publishes how those nine points split across its four parts.

Part A · 1 point

Describe a biological concept, process or model.

Part B · 3 points

Identify the experimental methods, or describe the data you are given.

Part C · 3 points

Identify methods, analyze the data, or run a calculation.

Part D · 2 points

Make a prediction and justify it.

Six of the nine sit in Parts B and C, which are experimental method and data analysis. Only two go to the prediction most students practice. The second question is 4 points, one for each part, and all four are about the model you are handed: describe it, explain the relationships in it, represent a relationship within it, then connect it to a larger biological idea.

Both questions are worth 9 points and share a title. Point splits published by College Board, Course and Exam Description p. 208.

One thing worth knowing before you start reviewing. Two exam questions share the title Interpreting and Evaluating Experimental Results, and they split their nine points differently. The version with a graph to construct puts four of its nine points on drawing that graph, and it belongs to Units 3, 5, 7 and 8. Unit 6 gets the other one, which has no graph-construction part at all. Practicing graph construction for this Progress Check is practicing the wrong question.

Where students lose the most points

These are not our guesses. College Board publishes the errors it sees on this unit, in the Unit 6 opener of the course and exam description, and five of the six below come straight from that list.

Blurring gene and allele

College Board’s first named error for this unit. A gene is the sequence; an allele is one version of it. Answers that use the two interchangeably lose the point even when the biology behind them is right.

Skipping the reasoning step

College Board’s own account of where free-response points go: students connect a change at the molecular level to a change in phenotype without saying why one causes the other. Naming the mutation and then naming a protein level is not an explanation on its own.

Saying a mutation denatured the protein

Named by College Board as a common error. Denaturation is a loss of shape caused by conditions such as heat or pH. A mutation changes the sequence, and through the sequence the structure, which is a different claim.

Calling a point mutation a frameshift

Also on College Board’s list, and the two are separate categories. A point mutation substitutes one nucleotide for another. A frameshift inserts or deletes one, which shifts the reading frame from there to the end.

Treating every mutation as harmful

College Board says outright that mutations can be beneficial, detrimental or neutral, and that which one depends on the environment. Silent mutations change no amino acid at all.

Mixing up promoter and operator

The promoter is where RNA polymerase binds, and College Board says so directly. A repressor binds elsewhere on the DNA and blocks transcription. College Board’s own phrase for that is negative regulatory molecules, and it is the safest wording for a free-response answer.

Where the real explanations already are

The answers you are looking for exist, and they are not on a flashcard site. College Board’s own description of Progress Checks says the multiple-choice questions come with rationales that explain the correct answer and each incorrect one, and that the free response comes with scoring information. That sits inside AP Classroom, against the same 25 or so questions you just answered.

Release is a teacher setting rather than something the platform hides from you, so the thing to do is ask. Once the scored version is open, the rationale on a question you got wrong is worth more than the letter would have been. Unit 6’s questions are written on College Board’s pairing of each topic with one skill, so a rationale points at which of the eight topics let you down, not just which option was incorrect.

How to work through this unit

For any operon question, answer two things in order: is the regulatory protein bound right now, and can RNA polymerase reach the promoter? Answer those two in that order and the rest of the question usually falls out of them.

For the free response, work backwards from the point split. Parts B and C of the 9-point question carry six of its nine points and both are about experimental method and data, so practice reading an unfamiliar setup and saying what was measured and what it shows before you practice predictions.

Once you have finished the Progress Check, put your raw score into our AP Biology exam score calculator to see roughly where that pace puts you on the 1–5 scale, and use the AP Biology Review for the full exam format and study plan.

Frequently asked questions

Quick answers, checked against College Board.

Does a Unit 6 Progress Check score predict my AP exam score?

No, and College Board says why. Progress Check questions are written on the pairing between a topic and one specific skill. Exam questions can pair any topic with any of the skills, so a Progress Check tells you how the unit went, not how May will go. They are formative by design.

How long is Unit 6 supposed to take?

College Board suggests about 18 to 20 class periods for Unit 6. That makes it the third-longest unit in the course, behind Natural Selection and Ecology, and roughly double the time it suggests for Heredity. It carries 12 to 16 percent of the multiple-choice section.

Are the Unit 6 free-response questions the same length as the real exam's?

Yes. Several Progress Checks give shortened versions of the free-response questions, and College Board says those exist to prepare students for the fuller questions on the exam. Unit 6 is not one of them: both of its free-response questions are full length.

Do you post AP Biology Unit 6 answers?

No. We explain the reasoning and the traps; we never publish AP Classroom answer keys. The explanations already exist anyway. College Board includes a rationale for the correct answer and for each incorrect one with every Progress Check multiple-choice question, inside AP Classroom, once your teacher releases the results.