Week 15 — Quiz (auto-graded) · Gene Regulation, Mutation & Biotechnology

Course: Introduction to Biology — General Biology I (BIOL 101) · Silver Oak University (fictional sample) · Prof. Castellano
Objective tested: Objective 8 — gene regulation (the lac operon); mutation types and their effects (silent / missense / nonsense / frameshift); the biotechnology toolkit (PCR copies, gel electrophoresis sorts — smaller fragments travel farther, recombinant DNA/plasmids, CRISPR); DNA fingerprinting.
Points: 10 (1 each) · Assignment group: Quizzes (10% of grade) · Due: end of Module 15.

This is the human-readable quiz with its vetted answer key and feedback. The import-ready Classic QTI is in F-quiz-week-15-qti.xml (generated by the shared validated script — parses with 10 items, every single-answer item exactly one correct). The reusable item-bank entries and the Canvas placement block are at the bottom of this file.

Blueprint

No trick questions; distractors target the Week 15 misconceptions named in the lecture outline.

Questions, key, and feedback

Q1 (MC). Every cell in your body contains the same DNA, yet a neuron and a skin cell look and behave very differently. The best explanation is that —
- A. skin cells have lost the genes that neurons use
- B. each cell type expresses (turns ON) only a subset of its genes — gene regulation ✅
- C. neurons contain extra DNA that skin cells lack
- D. the cells have completely different DNA sequences
Feedback: Same DNA, different genes ON. Every cell keeps the full genome; gene regulation controls which genes are expressed, and that's what makes a neuron a neuron and a skin cell a skin cell. (No genes are lost (A) or added (C), and the sequence is the same (D).)

Q2 (MC). In the lac operon, the genes that digest lactose are normally OFF because a repressor protein blocks transcription. What turns these genes ON?
- A. the presence of lactose, which pulls the repressor off the DNA ✅
- B. the complete absence of any sugar
- C. exposure to sunlight
- D. a mutation that destroys the DNA
Feedback: The lac operon is a thermostat: when lactose appears, it pulls the repressor off the DNA, the block is lifted, and the lactose-digesting genes switch ON. No lactose → repressor stays on → genes OFF (don't build tools you don't need).

Q3 (Matching). Match each mutation type to the effect that best describes it. (All involve a change to the DNA.)
| Mutation type | Correct effect |
|---|---|
| Silent point mutation | Codon changes but still codes for the SAME amino acid; protein unchanged |
| Missense point mutation | Codon now codes for a DIFFERENT amino acid; one wrong building block |
| Nonsense point mutation | Codon becomes a STOP codon; protein is cut short (truncated) |
| Frameshift mutation | An inserted or deleted base shifts the whole reading frame downstream |
Feedback: The classic mix-ups: silent = no change to the amino acid (the code is redundant); missense = a different amino acid; nonsense = an early STOP (truncated protein); frameshift = an insertion/deletion that reframes every downstream codon because codons are read in threes.

Q4 (MC). Which statement about mutations is TRUE?
- A. Every mutation is harmful to the organism
- B. Mutations can be harmful, neutral, or beneficial ✅
- C. Mutations can never be passed on to offspring
- D. Mutations only occur in bacteria
Feedback: Not all mutations are bad. Many are neutral (silent), some are harmful (sickle-cell, many cancers), and a few are beneficial (lactase persistence; antibiotic resistance from a bacterium's view). Mutation is the raw material of variation and evolution.

Q5 (MC). A single DNA base change swaps one codon for another, but the new codon codes for the SAME amino acid, so the protein is completely unchanged. This is a —
- A. frameshift mutation
- B. nonsense mutation
- C. silent mutation ✅
- D. missense mutation
Feedback: A silent mutation changes the DNA but not the amino acid, because the genetic code is redundant (several codons can specify the same amino acid). The protein — and the organism — are unaffected.

Q6 (MC). During gel electrophoresis, three DNA fragments are run: 500 bp, 2000 bp, and 4000 bp. Which fragment travels FARTHEST from the well?
- A. the 4000-bp fragment, because it is largest
- B. the 500-bp fragment, because smaller fragments travel farther ✅
- C. they all travel exactly the same distance
- D. the 2000-bp fragment, because it is in the middle
Feedback: Smaller fragments travel farther. The gel is a mesh: small fragments slip through and migrate far, while large fragments snag and stay near the wells. "Small and fast runs far." (Verified for this week's lab: 500 bp travels farther than 2000 bp, which travels farther than 4000 bp.)

Q7 (MC). A scientist has only a trace of DNA and needs millions of copies of it before she can analyze it. Which tool makes many copies of a DNA segment?
- A. gel electrophoresis, which copies DNA
- B. PCR (polymerase chain reaction), which copies (amplifies) DNA ✅
- C. a microscope, which copies DNA
- D. a plasmid, which sorts DNA by size
Feedback: PCR copies; the gel sorts. PCR amplifies a tiny sample into millions of copies. (A and C misstate what those tools do; a plasmid is a cloning vector, not a sorter (D).) Often you copy with PCR first, then sort on a gel.

Q8 (True / False). "In gel electrophoresis, larger DNA fragments travel farther from the wells than smaller fragments."
- True
- False ✅
Feedback: False. It's the opposite — smaller fragments travel farther; larger ones get tangled in the gel mesh and stay close to the wells.

Q9 (Multiple answer — select all that apply). Which of the following correctly describe a biotechnology tool and what it does?
- A. PCR makes millions of copies of a DNA segment ✅
- B. Gel electrophoresis sorts DNA fragments by size ✅
- C. CRISPR-Cas9 is used to edit (cut and change) DNA at a specific location ✅
- D. Recombinant DNA combines DNA from two different sources, often using a plasmid ✅
- E. Gel electrophoresis makes DNA fragments larger so they are easier to see
Feedback: A–D are all correct: PCR copies, the gel sorts, CRISPR edits, recombinant DNA splices. E is false — a gel separates fragments by size; it does not make them larger.

Q10 (MC). On a DNA gel, the crime-scene sample shows bands at exactly the same positions as Suspect 2's bands, but NOT the same as Suspect 1's bands. What is the best conclusion?
- A. The crime-scene DNA matches Suspect 2, whose band pattern lines up with it ✅
- B. The crime-scene DNA matches Suspect 1, because suspects always match
- C. No conclusion is possible from a gel
- D. The crime-scene DNA must belong to both suspects equally
Feedback: In DNA fingerprinting, you identify a match by checking whether the band patterns line up. The crime-scene bands align with Suspect 2, so Suspect 2's DNA is the best match. (This is exactly the logic of this week's lab.)

Answer key (quick reference)

Quality gate (self-checked): each single-answer item (Q1, Q2, Q4, Q5, Q6, Q7, Q8, Q10) has exactly one correct option; the multiple-answer item (Q9) marks the four true tool descriptions (A, B, C, D) and requires E to be left unselected; the matching item (Q3) pairs four mutation types to four distinct effects; no item asserts a fact outside the Week 15 course definitions. Week 15 is conceptual (no curriculum arithmetic in the quiz), so the key is a vetted, one-correct-per-single-answer key rather than a numeric gate. The one quantitative claim used — smaller DNA fragments migrate farther than larger ones (500 bp > 2000 bp > 4000 bp by distance) — and the band-matching scenario were re-verified with a scratchpad logic check (lab logic gate: PASS) before shipping.

Item-bank entries (for variants + the midterm/final)

All ten items are tagged course=BIOL101 · week=15 · objective=8 · topic=regulation-mutation-biotech and deposited in Item Bank: Week 15 — Gene Regulation, Mutation & Biotechnology. The cumulative final (Week 16) and the per-term variant updates draw fresh items from this bank. (Tags: q1 gene-regulation, q2 lac-operon, q3 mutation-type-match, q4 mutation-effects-vary, q5 silent-mutation, q6 gel-smaller-farther, q7 pcr-vs-gel, q8 gel-misconception-tf, q9 biotech-toolkit, q10 dna-fingerprint-match.)

Canvas placement block

canvas_object   = Quizzes::Quiz
title           = "Week 15 Quiz — Gene Regulation, Mutation & Biotechnology"
assignment_group = "Quizzes"
points_possible = 10
grading_type    = points
due_offset_days = 6        # 6 days after module start
published       = true
shuffle_answers = true
provenance      = "~ Prof. Castellano's edition · Fall 2026 · built with thecoursemaker.com"