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7th grade Predict traits with a Punnett square worksheet

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Predict traits with a Punnett square

Grade 7 Science Worksheet

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Circle the best answer, or write your answer on the line.

  1. Ari makes a Punnett square for Vv × Vv pea plants. What is the chance an offspring has violet flowers, as a percent?

  2. Bo makes a Punnett square for Tt × Tt pea plants. What is the chance an offspring is dwarf, as a percent?

  3. Esme makes a Punnett square for YY × Yy pea plants. What is the chance an offspring seed is yellow, as a percent?

  4. V = violet (dominant), v = white (recessive). Cross: VV × vv. Jun predicts the offspring of a VV × vv pea cross. What will they look like?

    • All violet, each with the letters Vv
    • Half violet and half white
    • All pale violet, a blend of the two colors
    • All white, since white was hidden

  5. T = tall (dominant), t = dwarf (recessive). Cross: Tt × tt. Kira predicts the offspring of a Tt × tt pea cross. Which ratio of tall to dwarf is expected?

    • Medium-height plants
    • 1 tall to 1 dwarf
    • 1 TT to 2 Tt to 1 tt
    • 3 tall to 1 dwarf

  6. Y = yellow (dominant), y = green (recessive). Cross: Yy × Yy. Luz predicts the seed colors from a Yy × Yy pea cross. Which ratio of yellow to green is expected?

    • Yellow-green seeds
    • 3 yellow to 1 green
    • 1 yellow to 1 green
    • 1 YY to 2 Yy to 1 yy

  7. Every offspring Vv, violet flowers. V = violet (dominant), v = white (recessive). Milo reads that every offspring of a pea cross is violet with the letters Vv. Which parents fit?

    • VV × VV: two pure violet parents
    • VV × vv: pure violet and white
    • vv × vv: two white parents
    • Vv × Vv: two mixed parents

  8. Ren grows seedlings from a Tt × Tt cross. The first three are tall. What is the chance the next one is dwarf?

    • Zero: this cross makes tall plants
    • 1 in 4, the same as for each seedling
    • 1 in 3, since three are done
    • Certain: one in four seedlings has to be dwarf

  9. Tala has 4 seeds from one Rr × Rr cross. Must exactly 3 of them be round?

    • No: each seed has a 3 in 4 chance, so counts vary
    • Yes: the square promises 3 round in each 4
    • Yes: unless a seed blends into a new shape
    • No: the 4 seeds will match each other

  10. Zee grows plants from a Vv × vv cross. The first two have white flowers. What is the chance the third is violet?

    • 1 in 2, the same as each time
    • 1 in 4, as in a Vv × Vv cross
    • Above 1 in 2, to balance the two white
    • Zero, since white keeps showing up
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7th grade Predict traits with a Punnett square worksheet – printable
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About this worksheet

Predict traits with a Punnett square. Every version has 10 questions, and the answer key prints on the second page.

What your child will learn

  • I can fill a Punnett square for one gene with two forms and read which trait each box shows.
  • I can give the chance of a trait as a percent, and the expected number out of many offspring.
  • I can work backward from offspring to parents, use a test cross, and explain why real counts land near, not on, the square's ratio.

Standard: MS-LS3-2

Words to know

gene, allele: A gene is an instruction for a trait; alleles are its forms (V or v)

dominant: The form that shows when at least one copy is there (capital letter)

recessive: The form that shows only with two copies (two small letters)

genotype / phenotype: The letter pair / the trait you can see

homozygous / heterozygous: Two same letters (VV, vv) / two different letters (Vv)

Punnett square: A grid that shows every way the parents' letters can pair up

test cross: Crossing an unknown plant with a vv plant to find its letters

Common mistakes

Your child filled a Punnett box with both letters from one parent. Each box takes one letter from the top and one from the side. Try covering the other boxes and reading across and down together.

Your child thought a plant with one dominant and one recessive letter (such as Vv) shows the recessive trait. With a dominant letter present, the dominant trait shows. Ask your child what the capital letter means.

Your child expected the two traits to mix into an in-between, such as pale violet or medium height. For Mendel’s pea traits the forms do not blend: each plant shows one trait or the other. Ask your child which form a Vv plant shows.

Questions parents ask

What is the most common mistake with predict traits with a punnett square?

Your child filled a Punnett box with both letters from one parent. Each box takes one letter from the top and one from the side. Try covering the other boxes and reading across and down together.

Are these 7th grade science worksheets free to print?

Yes. All 6 printable versions at each level are free to print, with the answer key, and no account is needed.

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