Predicting Inherited Traits · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.
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Using inheritance models

Science · Ecosystems & Habitats · ages 13-14
Name ______________________   Date ____________

  1. In a two-allele model with complete dominance, what do we call the allele that determines the phenotype in a mixed pair?

    • Recessive
    • Dominant allele
    • Genotype

  2. What are different versions of the same gene called?

    • Alleles
    • Genes
    • Chromosomes

  3. In a two-allele model where B is completely dominant over b, genotype Bb shows the recessive trait.

    Circle one:   True   False

  4. Use a four-box Punnett square for BB x bb. How many boxes contain at least one B allele?

    Answer: ______________

  5. In a Punnett square for Bb x Bb, how many of the four boxes contain bb?

    • 1
    • 2
    • 3

  6. A pea plant has genotype Tt. What does genotype describe here?

    • The observable height of the plant after it has grown.
    • The allele combination for the gene.
    • The total number of chromosomes in each plant cell.

  7. For pea height, T is dominant for tall and t is recessive for short. A Tt x Tt cross gives TT, Tt, Tt and tt. Among 100 offspring, how many are expected to be tall?

    Answer: ______________

  8. In the lesson's cystic-fibrosis model, two parents are Cc carriers. Priya says a cc child is impossible and the same one-gene model fully predicts human eye color. Which correction fits both claims?

    • Carriers cannot pass c; eye color needs several genes.
    • Carriers can pass c; eye color follows exactly the same one-gene rules as this cystic-fibrosis model.
    • Each carrier can pass c to a child; human eye color involves several genes.
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Answer key

For grown-ups. Fold this page away before handing over the rest.

Using inheritance models W1-mt_o7FJPDsHiW-s1

  1. Dominant allele · Dominant names the allele relationship described. Genotype names the allele combination, not a kind of allele.
  2. Alleles · Alleles are versions of a gene. A gene is a section of DNA, and a chromosome carries many genes.
  3. False · Bb shows the dominant trait in this model. The recessive trait appears with bb.
  4. 4 · The BB parent contributes B in every pairing, and the bb parent contributes b. All four boxes are Bb and contain B.
  5. 1 · The four pairings are BB, Bb, Bb and bb. Only one combines b from both parents.
  6. The allele combination for the gene. · Tt identifies the allele combination, its genotype. Tall is the phenotype in the stated pea-height model.
  7. 75 · Three of four equally likely pairings have at least one T. The expected tall count is 3/4 x 100 = 75, though the actual count can differ.
  8. Each carrier can pass c to a child; human eye color involves several genes. · Each Cc carrier can pass c, so two carriers can have a cc child. Several genes affect human eye color, so the same one-gene model does not fully predict it.
Worksheet · LightMySky