Week 12 — Blends, Blood Types, and Carriers: The Patterns of Inheritance Report

Assignment 11 of the term — work three non-Mendelian crosses into counts, explain what each heterozygote shows, and tell a friend why a family's sons can show a trait their fathers do not.

This adaptive assignment uses a coaching dialogue to help you turn a first attempt into a clear, evidence-based report on this week's patterns of inheritance. 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 pink cross, the ABO alleles, and the carrier cross together. It builds on Week 11's Punnett squares and product rule, which work the same way here.

The task

The non-Mendelian crosses are the discipline's canonical crosses with the arithmetic shown. In each problem below, the total number of offspring or children is illustrative, chosen for this assignment, and the probabilities come from the crosses:

• RW × RW (two pink snapdragons): 1 red : 2 pink : 1 white, so P(pink) = 1⁄2;
• the ABO gene: three common alleles, Iᴬ, Iᴮ, and i;
• Iᴬi × Iᴮi (a type A parent and a type B parent): AB, A, B, and O, each 1⁄4;
• XᴬXᵃ × XᴬY (a carrier mother and an unaffected father): 1⁄2 of sons affected, 0 of daughters affected, and 1⁄4 of all children affected.

Work these four problems, showing your arithmetic:

1. Two pink snapdragons (RW × RW) give P(pink) = 1⁄2. Among 100 illustrative offspring of such crosses, how many pink offspring do the odds predict?
2. The ABO gene has three common alleles, and each person carries two. Counting the 3 homozygous genotypes (IᴬIᴬ, IᴮIᴮ, ii) and the 3 heterozygous genotypes (IᴬIᴮ, Iᴬi, Iᴮi), how many ABO genotypes are there?
3. A type A parent (Iᴬi) and a type B parent (Iᴮi) each pass i with probability 1⁄2, so P(O) = 1⁄2 × 1⁄2 = 1⁄4. Across 80 illustrative children of such couples, how many type O children do the odds predict?
4. In the carrier cross XᴬXᵃ × XᴬY, 1⁄4 of all children are affected by the X-linked recessive trait. Across 60 illustrative children of such couples, how many affected children do the odds predict?

Beside each answer, add one brief interpretation:

• Problem 1: explain incomplete dominance as a blend partway between the parents, and explain why the color ratio for RW × RW is 1 red : 2 pink : 1 white, matching the genotype ratio, rather than 3:1.
• Problem 2: explain why Iᴬ and Iᴮ are codominant, naming what a type AB red blood cell carries, and explain why type O is common even though i is recessive.
• Problem 3: explain how two parents who show A and B can have a type O child, and name the probability rule that gives P(O).
• Problem 4: explain why every affected child in the carrier cross is a son, using where a son's X comes from and what hemizygous means, and say why a male cannot be a carrier.

Explain it to a non-expert

A friend is drawing a family chart for a made-up trait and notices that, across three generations, only sons show it and no father who shows it has passed it to his son. The friend asks, "Does that mean the dads pass it down?" Write a 3–5 sentence message that explains, in everyday words, where a son's X chromosome comes from and how a mother can carry the allele without showing it, connects it to the carrier cross, and names one limit, including that a small family chart cannot rule out every other pattern and that the counts in your report are illustrative. Explain any technical term in everyday words. More than one good answer is possible.

For a different, ungraded example, imagine a friend asking why a sprint leaves your legs burning when a slow jog does not. Model answer: "Your muscles run on a fuel your cells remake from food, and the best way to remake it needs oxygen. In a sprint your muscles need fuel faster than your blood can bring oxygen, so they switch to a quick backup that works without it. That backup makes much less fuel, so you tire fast. This explains why a sprint feels harder, but it does not tell you exactly how long you can keep it up, which differs from person to person."

Use that pattern for your friend's family chart, with your own wording and evidence.

Part 1 — Student instructions

1. Draft all four answers, the four brief interpretations, and your message to your friend 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 patterns of inheritance. 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 trait's inheritance.

ASSIGNMENT: Work through these four problems in order, one at a time. Do not invent, replace, or reorder a problem. The data: the non-Mendelian crosses, the discipline's canonical crosses with the arithmetic shown. RW x RW gives 1 red : 2 pink : 1 white, so P(pink) = 1/2. The ABO gene has three common alleles, I^A, I^B, and i. I^Ai x I^Bi gives AB, A, B, and O, each 1/4. X^AX^a x X^AY gives 1/2 of sons affected, 0 of daughters affected, and 1/4 of all children affected. The totals in the problems are illustrative. In this prompt, "x" between two genotypes means "crossed with" and "x" between two numbers means "times"; the caret marks a raised letter.
PROBLEM P1: Two pink snapdragons (RW x RW) give P(pink) = 1/2. Among 100 illustrative offspring of such crosses, how many pink offspring do the odds predict?
PROBLEM P2: The ABO gene has three common alleles, and each person carries two. Counting the 3 homozygous genotypes (I^AI^A, I^BI^B, ii) and the 3 heterozygous genotypes (I^AI^B, I^Ai, I^Bi), how many ABO genotypes are there?
PROBLEM P3: A type A parent (I^Ai) and a type B parent (I^Bi) each pass i with probability 1/2, so P(O) = 1/2 x 1/2 = 1/4. Across 80 illustrative children of such couples, how many type O children do the odds predict?
PROBLEM P4: In the carrier cross X^AX^a x X^AY, 1/4 of all children are affected by the X-linked recessive trait. Across 60 illustrative children of such couples, how many affected children do the odds predict?
After the four answers, I must briefly interpret each one: for P1, incomplete dominance as a blend partway between the parents, plus why RW x RW gives 1 red : 2 pink : 1 white, matching the genotype ratio, rather than 3:1; for P2, why I^A and I^B are codominant, naming what a type AB red blood cell carries, plus why type O is common even though i is recessive; for P3, how two parents who show A and B can have a type O child, plus the probability rule that gives P(O); for P4, why every affected child in the carrier cross is a son, using where a son's X comes from and what hemizygous means, plus why a male cannot be a carrier. I must then write a 3-5 sentence message to a friend who is drawing a family chart for a made-up trait in which only sons show it, explaining in everyday words where a son's X chromosome comes from and how a mother can carry the allele without showing it, connected to the carrier cross, and naming one limit, including that a small family chart cannot rule out every other pattern and that my counts are illustrative. 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 friend only with P4, not again with P1-P3.
COMPUTATION UNITS: A correct pink count, genotype count, type O count, or affected 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 every genotype, or equivalent correct notation.
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 why every affected child is a son, with the son's X from his mother and no male carrier, AND a friend's message that explains the mother-to-son path in everyday words and names a limit = 2. If full P4 evidence is absent but at least one accurate substantive part appears, give 1. No accurate reasoning = 0; giving 3 pink : 1 white, calling the pink snapdragon codominant, saying type O is dominant, saying a male can be a carrier, or saying an affected son got the allele from his father 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 friend's 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 friend 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 inheritance report, and the share link.
COPY EVERYTHING ABOVE THIS LINE

Deliverables

Submit these three items in the assignment entry:

• your revised inheritance report with all four answers, their brief interpretations, and your message to your friend — written, or recorded as audio or video with a transcript, or as labelled hand-drawn Punnett squares 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 12 skills — turning incomplete dominance, multiple alleles, and X-linked crosses into predicted counts, explaining what a heterozygote shows under each pattern, and explaining why a carrier mother's sons, not her daughters, show an X-linked recessive trait — 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 friend. 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 inheritance 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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