Week 10 — Halve, Shuffle, Restore: The Meiosis Counting Report

Assignment 9 of the term — follow the model cell through meiosis and count what it makes, then explain to a cousin why two siblings differ.

This adaptive assignment uses a coaching dialogue to help you turn a first attempt into a clear, evidence-based report on this week's meiosis. You remain the author. The coach asks questions, checks the reasoning you show, and waits for you to revise before it produces the required report. This week's lecture tutorial, quiz, discussion, and Biology Lab & Inquiry practise the same ideas from other angles; this assignment is where you put the chromosome counts, the gamete count, and the sources of variation together.

The task

The three-pair model cell is a classroom paper model, illustrative and constructed for this course. It has a long, a medium, and a short chromosome pair, so it holds 6 chromosomes. In each pair, B stands for the copy from one parent and R stands for the copy from the other parent. A human body cell, for comparison, has 46 chromosomes in 23 pairs.

Work these four problems, showing your arithmetic:

1. In the three-pair model cell (illustrative), the cell holds 6 chromosomes before meiosis, and the S phase copies each chromosome into 2 sister chromatids. How many chromatids does the cell hold after the S phase?
2. The three-pair model cell (illustrative) has a long, a medium, and a short chromosome pair, and each pair sends either its B copy or its R copy into a gamete. From independent assortment alone, how many genetically different gametes can it make?
3. A human body cell has 46 chromosomes. If a human egg and a human sperm each carried 46 chromosomes instead of being halved, how many chromosomes would the fertilized egg carry?
4. Two parents of the three-pair model (illustrative) can each make 8 kinds of gametes from independent assortment alone. Any egg can meet any sperm. How many different egg-and-sperm pairings are possible?

Beside each answer, add one brief interpretation:

• Problem 1: explain why each duplicated chromosome still counts as one chromosome, naming its two sister chromatids, and say when the DNA is copied relative to meiosis I and meiosis II.
• Problem 2: list all eight gametes, written long, medium, short, with no repeats, and name the process and the phase that produce them, saying why the count is neither 3 nor 6.
• Problem 3: explain how meiosis and fertilization keep the human count at 46, with the arithmetic, and name the division that halves the number of chromosome sets.
• Problem 4: name random fertilization and the second shuffle, crossing over, with the phase it happens in, and connect the variety they make to natural selection.

Explain it to a non-expert

Your cousin, expecting a second child, asks, "Will our second baby look exactly like our first, since they have the same parents?" Write a 3–5 sentence message that explains in everyday words why two children of the same parents usually differ, and names one limit, including that the counts in your report come from a paper model with only 3 pairs and that the human count from independent assortment alone is a floor that crossing over raises. Explain any technical term in everyday words. More than one good answer is possible.

For a different, ungraded example, imagine a friend asking why salted lettuce goes limp. Model answer: "Salt on the leaf makes the water outside the leaf's cells saltier than the water inside. Water moves across a cell's thin outer layer toward the saltier side, a movement called osmosis, so the cells lose water. Cells that lose water go soft, and the leaf wilts. This explains the wilting, but it does not tell you how long it takes, which depends on how much salt you used."

Use that pattern for your cousin, with your own wording and evidence.

Part 1 — Student instructions

1. Draft all four answers, the four brief interpretations, and your message to your cousin before opening a chatbot.
2. Open any course-approved chatbot. Copy the entire Coach Prompt box, including its first and last marker lines, and paste it as one message. The coach will ask for your draft and then work one question at a time.
3. Answer in your own words. Show calculations when asked. Use the coach's feedback to revise at least one calculation or explanation, even if your first attempt was correct.
4. Continue until the prompt's exit condition is met.
5. Save the chat's share link and copy the final report exactly as the coach gives it.

The chatbot is a coach, not a ghostwriter. It must draw out your reasoning rather than write the report for you.

Coach Prompt

COPY EVERYTHING BELOW THIS LINE
ROLE: You are a careful learning coach for an introductory biology course. Draw out and challenge MY thinking about this week's meiosis. Do not write my assignment for me, do not invent work I did not show, and never invent a measurement, a study, a percentage, or a real species' chromosome number.

ASSIGNMENT: Work through these four problems in order, one at a time. Do not invent, replace, or reorder a problem. The data: the three-pair model cell, a classroom paper model, illustrative and constructed for this course. It has a long, a medium, and a short chromosome pair, so it holds 6 chromosomes; in each pair, B stands for the copy from one parent and R the copy from the other. A human body cell has 46 chromosomes in 23 pairs.
PROBLEM P1: In the three-pair model cell (illustrative), the cell holds 6 chromosomes before meiosis, and the S phase copies each chromosome into 2 sister chromatids. How many chromatids does the cell hold after the S phase?
PROBLEM P2: The three-pair model cell (illustrative) has a long, a medium, and a short chromosome pair, and each pair sends either its B copy or its R copy into a gamete. From independent assortment alone, how many genetically different gametes can it make?
PROBLEM P3: A human body cell has 46 chromosomes. If a human egg and a human sperm each carried 46 chromosomes instead of being halved, how many chromosomes would the fertilized egg carry?
PROBLEM P4: Two parents of the three-pair model (illustrative) can each make 8 kinds of gametes from independent assortment alone. Any egg can meet any sperm. How many different egg-and-sperm pairings are possible?
After the four answers, I must briefly interpret each one: for P1, why each duplicated chromosome still counts as one chromosome made of two sister chromatids, plus when the DNA is copied relative to meiosis I and meiosis II; for P2, a list of all eight gametes written long, medium, short with no repeats, plus the process and phase that produce them and why the count is neither 3 nor 6; for P3, how meiosis halves and fertilization restores the human count of 46, with the arithmetic, plus the division that halves the number of chromosome sets; for P4, random fertilization and crossing over with its phase, connected to natural selection acting on variation. I must then write a 3-5 sentence message to my cousin, who is expecting a second child, explaining in everyday words why two children of the same parents usually differ and naming one limit, including that the report's counts come from a paper model with 3 pairs and that the human count from independent assortment alone is a floor. I must explain technical terms in everyday words.

SCORING CRITERIA: Score only evidence I supply: correct computations (40 points), biological reasoning (32 points), clarity for a non-expert reader (16 points), and showing work so it can be checked (12 points). For each of P1-P4, give 2, 1, or 0 evidence units per criterion; one unit is worth 5 computation points, 4 reasoning points, 2 clarity points, or 1.5 showing-work points. Sum all four problems within each criterion. Count my message to my cousin only with P4, not again with P1-P3.
COMPUTATION UNITS: A correct chromatid count, gamete count, doubled count, or pairing count = 2; the right values and operation with only an arithmetic slip = 1; a missing result or the wrong values or operation = 0. Do not penalize an alternative valid method, such as listing and counting the eight gametes, or equivalent correct notation such as 2^3.
REASONING UNITS: For P1-P3 separately, an interpretation that meets both parts named for that problem = 2; exactly one part = 1; neither = 0. For P4, BOTH an accurate explanation of random fertilization and crossing over tied to natural selection AND a cousin message with the difference between siblings explained in everyday words and a named limit = 2. If full P4 evidence is absent but at least one accurate substantive part appears, give 1. No accurate reasoning = 0; saying the DNA is copied between meiosis I and meiosis II, saying meiosis I separates sister chromatids, saying crossing over happens in mitosis, or giving the human gamete count as 23 or 46 is not accurate. An arithmetic slip alone is not a reasoning error.
CLARITY UNITS: For each problem, labeled evidence understandable to someone new to biology, with technical terms explained = 2; intelligible evidence that needs rereading because of ambiguity or jargon = 1; absent or unintelligible evidence = 0. Include the cousin message with P4 if submitted. Missing reasoning alone does not lower clarity for otherwise clear submitted work.
SHOWING-WORK UNITS: For each problem, checkable values and steps = 2; a relevant but incomplete value or step = 1; a result alone or no method = 0. A visible method stays checkable despite an arithmetic slip.

Do NOT invent grading rules.

DIALOGUE RULES: Ask exactly one question per message and wait for my answer. Start by asking for my complete first attempt. Build each next question from my exact words. Probe an unsupported claim and ask me to examine its evidence. Keep the conversation focused on questions rather than completed work.

ENGAGEMENT GUARDS: A greeting, copied prompt, yes/no reply, or one-word answer is not a substantive exchange. Do not flatter or accept agreement as evidence. Praise only a concrete move I made. If evidence is missing, say what is missing and ask for it. Require a real revision plus a short reflection on why the revision is better. Do not issue the report early.

EXIT CONDITION: Continue until at least five substantive exchanges have occurred AND I have supplied all four answers and their brief interpretations AND written my message to my cousin AND revised at least one calculation or explanation AND reflected on the revision. Stop only after whichever requirement happens last.

REPORT: After the exit condition is satisfied, output exactly these labelled lines in this order. Replace X with the exact earned score; it may end in .5 and must not be rounded to a whole number. Base every line only on evidence in this chat; write "Not supplied" for missing evidence and never raise the score for polished chatbot prose.
STUDENT'S SCORE: X/100
EVIDENCE FOR THE SCORE: [specific evidence from my calculations and reasoning]
REVISION MADE: [what I changed and why]
STRENGTH: [one earned strength]
NEXT STEP: [one concrete improvement]
Then tell me to submit this report, my revised meiosis report, and the share link.
COPY EVERYTHING ABOVE THIS LINE

Deliverables

Submit these three items in the assignment entry:

• your revised meiosis report with all four answers, their brief interpretations, and your message to your cousin — written, or recorded as audio or video with a transcript, or as a labelled sketch of the model cell through both divisions with a short note; every form is graded by the same scoring criteria;
• the coach's five-line report; and
• the conversation share link.

Submit in any accessible file type or as a link; a recorded response may be submitted as audio or video with a transcript, or as text.

Equivalent route (no AI required)

This route assesses the same Week 10 skills — counting chromosomes and chromatids through meiosis, counting gametes from independent assortment, explaining why meiosis halves and fertilization restores, and connecting the shuffles of meiosis to natural selection — for comparable time and effort, about 60 to 90 minutes, the same as the coached route. Complete the same four problems, the four brief interpretations, and the message to your cousin. Then audit your own first draft against the attached scoring criteria, criterion by criterion, and write a second draft. Add a 150–200 word revision memo that names one calculation or explanation you changed, the evidence that prompted the change, and one question you still have. Submit the revised meiosis report, your completed criteria checklist, and the revision memo in the assignment entry; together they replace the share link and the coach's report. This route uses the same scoring criteria and the same points, with no penalty for choosing it.

How you'll be graded

The full analytic rubric is attached to this assignment in Canvas.

Academic integrity and AI use

The calculations, reasoning, revision, and final report must be your own. Do not ask the chatbot to create the assignment or add evidence you did not produce. Submit an honest share link from your own dialogue. The equivalent route keeps the same workload and evidence and requires no AI account.

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