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9th grade Two-trait crosses with a 4 by 4 square worksheet

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Two-trait crosses with a 4 by 4 square

Grade 9 Science Worksheet

NameDate

Circle the best answer.

  1. Read this first

    Use this

    Parent card (pea plant P, genotype Rryy). Seed shape gene: alleles R (round) and r (wrinkled). Seed color gene: alleles y (green) and y (green).

  2. Ren crosses two pea plants. Plant P has genotype Rryy. Which choice lists all the allele combinations plant P can pass on, one allele for each gene?

    • Ry and ry
    • Rr and yy, the plant's own gene pairs
    • RY and ry, with each capital kept with a capital
    • Ry, ry, RY and rY, as for a plant with Yy

  3. Use this

    Parent card (pea plant Q, genotype rrYy). Seed shape gene: alleles r (wrinkled) and r (wrinkled). Seed color gene: alleles Y (yellow) and y (green).

  4. Jun crosses two pea plants. Plant Q has genotype rrYy. Which choice lists all the allele combinations plant Q can pass on, one allele for each gene?

    • rr and Yy, the plant's own gene pairs
    • rY and ry
    • rY, ry, RY and Ry, as for a plant with Rr
    • RY and ry, with each capital kept with a capital

  5. Use this

    Allele combinations card. Parent 1 (genotype RrYy) can pass on 4 combinations: RY, Ry, rY and ry. Parent 2 (genotype RrYY) can pass on 2 combinations: RY and rY.

  6. Kira crosses a plant with RrYy and a plant with RrYY. How many boxes does the Punnett square have?

    • 4 boxes: 2 across and 2 down
    • 16 boxes: 4 across and 4 down
    • 6 boxes: 4 plus 2
    • 8 boxes: 4 across and 2 down

  7. Luz reads the filled square for RrYy × RrYy. What is the ratio of round yellow : round green : wrinkled yellow : wrinkled green?

    • 9 : 3 : 3 : 1
    • 1 : 1 : 1 : 1
    • 3 : 1
    • 1 : 3 : 3 : 9

  8. Chance card for RrYy × RrYy

    Seed shape and seed color sort independently. Chance of round seeds: 3/4. Chance of wrinkled seeds: 1/4. Chance of yellow seeds: 3/4. Chance of green seeds: 1/4. Table: One-trait chances; columns trait and chance; rows round, wrinkled, yellow, green.

  9. Tala crosses RrYy with RrYy. Seed shape and seed color sort independently. What is the chance that one offspring is round and yellow?

    • 3/2
    • 9/16
    • 3/16, the chance for one dominant trait and one recessive
    • 3/4, the chance for one trait

  10. Zee crosses RrYy with RrYy again. What is the chance that one offspring is wrinkled and green?

    • 1/4, the chance for one trait
    • 1/9, from the 9 in the ratio
    • 1/16
    • 1/2

  11. Ari crosses RrYy with RrYy once more. What is the chance that one offspring is round and green?

    • 3/16
    • 9/16, the chance of round and yellow
    • 1
    • 3/4, the chance of round alone

  12. Model data

    320 seeds from the cross RrYy × RrYy. The 16 boxes of the square are equally likely, and the expected boxes are round yellow 9, round green 3, wrinkled yellow 3 and wrinkled green 1. Table: Model total of seeds; columns group and boxes of 16; rows seeds in the model total, round yellow, round green, wrinkled yellow, wrinkled green.

  13. Bo reads a model total of 320 seeds from RrYy × RrYy. About how many seeds are expected to be wrinkled and green?

    • 80 seeds
    • 20 seeds
    • 180 seeds
    • 1 seed

  14. Model data

    160 seeds from the cross RrYy × RrYy. The 16 boxes of the square are equally likely, and the expected boxes are round yellow 9, round green 3, wrinkled yellow 3 and wrinkled green 1. Table: Model total of seeds; columns group and boxes of 16; rows seeds in the model total, round yellow, round green, wrinkled yellow, wrinkled green.

  15. Esme reads a model total of 160 seeds from RrYy × RrYy. About how many seeds are expected to be round and green?

    • 90 seeds
    • 30 seeds
    • 120 seeds
    • 3 seeds

  16. Model data

    64 seeds from the cross RrYy × RrYy. The 16 boxes of the square are equally likely, and the expected boxes are round yellow 9, round green 3, wrinkled yellow 3 and wrinkled green 1. Table: Model total of seeds; columns group and boxes of 16; rows seeds in the model total, round yellow, round green, wrinkled yellow, wrinkled green.

  17. Pia reads a model total of 64 seeds from RrYy × RrYy. About how many seeds are expected to be wrinkled and yellow?

    • 36 seeds
    • 3 seeds
    • 12 seeds
    • 48 seeds
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9th grade Two-trait crosses with a 4 by 4 square worksheet – printable
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About this worksheet

Two-trait crosses: the four allele combinations, the 4 by 4 square and 9 : 3 : 3 : 1. Every version has 10 questions, and the answer key prints on the second page.

What your child will learn

  • I can list the four allele combinations a plant with RrYy can pass on (RY, Ry, rY, ry), one allele for each gene, and say why there are four: 2 × 2.
  • I can list the combinations for a plant with a pair of the same alleles in one gene (RrYY gives RY and rY; Rryy gives Ry and ry), and say how many boxes a cross needs (4 × 4 = 16, 4 × 2 = 8, 2 × 2 = 4).
  • I can say that the shape gene and the color gene sort independently when they are on different chromosomes, so any shape allele can go with any color allele (Ry is possible, not only RY and ry).
  • I can fill a box of a 4 by 4 square by reading one combination from the top and one from the side, giving one pair of letters for each gene.
  • I can read a genotype as a phenotype (one capital letter in a gene is enough for its dominant trait) and count the boxes of each phenotype: round yellow 9, round green 3, wrinkled yellow 3, wrinkled green 1.
  • I can say the phenotype ratio is 9 : 3 : 3 : 1, that each trait alone is still 3 : 1 (12 round boxes and 4 wrinkled, 12 yellow and 4 green), and that 9 : 3 : 3 : 1 does not apply to every cross.

Standard: HS-LS3-3

Words to know

gene: A stretch of DNA that carries the plan for one trait, such as seed shape

allele: One form of a gene, such as R for round or r for wrinkled

genotype: The pair of alleles a plant has for a gene, such as Rr

phenotype: The trait you can see, such as round seeds

dominant: An allele whose trait shows when only one copy is there

recessive: An allele whose trait shows only with two copies

dihybrid cross: A cross that follows two genes at once, such as seed shape and seed color

allele combination: One allele for each gene, such as Ry: what a parent passes on

Common mistakes

Your child listed the plant's own gene pairs, such as Rr and Yy, instead of the allele combinations. A combination takes one allele from each gene. Ask your child to pair each shape allele with each color allele.

Your child kept capital letters together and small letters together, as RY and ry. When the genes are on different chromosomes, each shape allele can go with either color allele. Ask your child whether Ry is possible.

Your child used 3 : 1 for both traits together. Each trait alone follows 3 : 1, but two traits together make four groups, 9 : 3 : 3 : 1. Ask your child to count the boxes for each pair of traits.

Questions parents ask

What is the most common mistake with two-trait crosses with a 4 by 4 square?

Your child listed the plant's own gene pairs, such as Rr and Yy, instead of the allele combinations. A combination takes one allele from each gene. Ask your child to pair each shape allele with each color allele.

Are these 9th 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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