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

6 printable versionsBuilding Confidence10 questions · answer keyFree · no account

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Two-trait crosses with a 4 by 4 square

Grade 9 Science Worksheet - Building Confidence

NameDate

Circle the best answer.

  1. Read this first

    Use this

    Parent card (pea plant, genotype RrYy). Seed shape gene: alleles R (round) and r (wrinkled). Seed color gene: alleles Y (yellow) and y (green). Table: Parent card; columns gene and alleles in the plant; rows seed shape, seed color.

  2. Ari reads a parent card for one pea plant. Which choice lists all the allele combinations this plant can pass on, one allele for each gene?

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

  3. Use this

    Parent card (pea plant, genotype RrYY). Seed shape gene: alleles R (round) and r (wrinkled). Seed color gene: alleles Y (yellow) and Y (yellow). Table: Parent card; columns gene and alleles in the plant; rows seed shape, seed color.

  4. Bo reads a parent card for another pea plant. Which choice lists all the allele combinations this plant can pass on, one allele for each gene?

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

  5. Use this

    Parent card (pea plant, genotype RrYy). The seed shape gene and the seed color gene are on different chromosomes. The combination in question is Ry: R from the seed shape gene and y from the seed color gene. Table: Parent card; columns gene and alleles in the plant; rows seed shape, seed color.

  6. The genes for seed shape and seed color are on different chromosomes. Esme asks why a plant with RrYy can pass on the combination Ry. What is the reason?

    • Ry appears because y is dominant over Y
    • The plant passes on Rr as one unit and Yy as one unit
    • The two genes sort independently, so R can go with either Y or y
    • R stays with Y, so RY and ry are the combinations passed on

  7. Jun fills in the square for RrYy × RrYy. Which genotype goes in the blank box?

    • RrYy (R: one capital, one small; Y: one capital, one small)
    • Rryy (R: one capital, one small; Y: two small)
    • rryy (R: two small; Y: two small)
    • RRyy (R: two capital; Y: two small)

  8. Luz fills in one more box of the square for RrYy × RrYy. Which genotype goes in the blank box?

    • rrYy (R: two small; Y: one capital, one small)
    • RrYy (R: one capital, one small; Y: one capital, one small)
    • rryy (R: two small; Y: two small)
    • rrYY (R: two small; Y: two capital)

  9. Use this

    Trait card for pea seeds, letter and seed trait. R: round (dominant). r: wrinkled (recessive). Y: yellow (dominant). y: green (recessive). Plant genotype: rrYy.

  10. Noah reads the same trait card. What do the seeds of a plant with genotype rrYy look like?

    • Round and yellow
    • Wrinkled and yellow
    • Wrinkled and green
    • Round and green

  11. Use this

    Trait card for pea seeds, letter and seed trait. R: round (dominant). r: wrinkled (recessive). Y: yellow (dominant). y: green (recessive). Plant genotype: Rryy.

  12. Pia reads the trait card once more. What do the seeds of a plant with genotype Rryy look like?

    • Round and yellow
    • Wrinkled and green
    • Round and green
    • Wrinkled and yellow

  14. Ren reads the filled square for RrYy × RrYy. How many of the 16 boxes show wrinkled, green seeds?

    • 9 boxes
    • 4 boxes
    • 1 box
    • 3 boxes

  15. Tala reads the same filled square. How many of the 16 boxes show round, yellow seeds?

    Use the picture in question 8.

    • 9 boxes
    • 1 box
    • 12 boxes
    • 3 boxes

  16. Zee reads the same filled square. How many of the 16 boxes show wrinkled, yellow seeds?

    Use the picture in question 8.

    • 3 boxes
    • 4 boxes
    • 1 box
    • 9 boxes
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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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