PencilGo

Grade 9 · Science · Biology

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

6 printable versionsChallenge Me10 questions · answer keyFree · no account

Level: Building Confidence · On Level · Challenge Me

When it’s done, scan the sheet with your phone and PencilGo marks it and picks the next one. Create a free account

Version
Print

Two-trait crosses with a 4 by 4 square

Grade 9 Science Worksheet - Challenge Me

NameDate

Circle the best answer.

  1. Ren test-crosses a round yellow plant (RrYy) with a wrinkled green plant (rryy). What phenotype ratio does the square predict?

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

  2. Read this first

    Test cross (model data)

    Plant X, a round yellow plant of unknown genotype, crossed with a wrinkled green plant (rryy). Offspring: 26 round yellow, 24 round green, 25 wrinkled yellow, 25 wrinkled green. Total: 100. Table: Test cross counts (model data); columns offspring and number of plants; rows round yellow, round green, wrinkled yellow, wrinkled green, total.

  3. Jun reads the model counts from a test cross of plant X with a wrinkled green plant (rryy). Which genotype is plant X?

    • RrYy (R: one capital, one small; Y: one capital, one small)
    • RRYy (R: two capital; Y: one capital, one small)
    • RRYY (R: two capital; Y: two capital)
    • RrYY (R: one capital, one small; Y: two capital)

  4. Test cross (model data)

    Plant X, a round yellow plant of unknown genotype, crossed with a wrinkled green plant (rryy). Offspring: 51 round yellow, 0 round green, 49 wrinkled yellow, 0 wrinkled green. Total: 100. Table: Test cross counts (model data); columns offspring and number of plants; rows round yellow, round green, wrinkled yellow, wrinkled green, total.

  5. Kira reads the model counts from another test cross of a round yellow plant X with a wrinkled green plant (rryy). Which genotype is plant X?

    • RrYY (R: one capital, one small; Y: two capital)
    • RrYy (R: one capital, one small; Y: one capital, one small)
    • RRYy (R: two capital; Y: one capital, one small)
    • RRYY (R: two capital; Y: two capital)

  6. Use this

    Mendel's F2 seed counts from separate one-trait crosses with garden peas. Seed shape: 5,474 round and 1,850 wrinkled. Seed color: 6,022 yellow and 2,001 green. Table: Mendel's one-trait counts; columns seed trait and number of seeds; rows round, wrinkled, yellow, green.

  7. Luz reads Mendel's one-trait counts. If seed shape and seed color sort independently, about what fraction of seeds in a two-trait cross are round and yellow?

    • About 1/16, since the recessive shares are close to 1/4
    • About 3/4, the share for either trait alone
    • About 9/16, since each share is close to 3/4
    • About 3/2, found by adding the two shares

  8. Model data

    160 plants from RrYy × RrYy. Counted: 92 round yellow, 29 round green, 31 wrinkled yellow, 8 wrinkled green. Expected from 9 : 3 : 3 : 1: 90, 30, 30 and 10. Table: Counted and expected (9 : 3 : 3 : 1 ratio); columns phenotype and counted and expected; rows round yellow, round green, wrinkled yellow, wrinkled green, total.

  9. Noah grows 160 plants from RrYy × RrYy and records model counts. Which statement fits the counts?

    • The counts are close to the expected 90, 30, 30 and 10, so they fit independent assortment
    • The counts do not fit, because no count matches its expected number exactly
    • The counts match 1 : 1 : 1 : 1, with 40 plants in each class
    • The counts do not fit, because wrinkled green should be 40, which is a quarter of the 160 plants

  10. Notebook for RrYy × RrYy

    Line 1: Each parent passes on 4 combinations. Line 2: The square has 4 × 4 = 16 boxes. Line 3: Round green fills 3 boxes. Line 4: The chance of round green is 3/4 + 1/4 = 1. Table: Notebook for RrYy × RrYy; columns line and what the notebook says; rows 1, 2, 3, 4.

  11. Tala's notebook is about one RrYy × RrYy cross. One line is wrong. Which fix is right?

    • Line 1 should say each parent passes on 2 combinations
    • Line 3 should say round green fills 9 boxes
    • Line 4 should multiply: 3/4 × 1/4 = 3/16
    • Line 2 should say the square has 4 + 4 = 8 boxes

  12. Notebook for a test cross

    Line 1: The cross is RrYy × rryy. Line 2: The rryy plant passes on only ry. Line 3: The square has 4 boxes, one for each combination of the RrYy plant. Line 4: The offspring come out 9 : 3 : 3 : 1. Table: Notebook for a test cross; columns line and what the notebook says; rows 1, 2, 3, 4.

  13. Zee's notebook is about a test cross. One line is wrong. Which fix is right?

    • Line 2 should say the rryy plant passes on RY, Ry, rY and ry
    • Line 1 should say the cross is RrYy × RrYy
    • Line 4 should say the offspring come out 1 : 1 : 1 : 1
    • Line 3 should say the square has 16 boxes

  14. Claim card

    RrYy × RrYy always gives 9 : 3 : 3 : 1. Both genes show simple dominance (R over r, Y over y). The seed shape gene and the seed color gene can be on different chromosomes or on the same one. Table: Claim card; columns claim and cross; rows always 9 : 3 : 3 : 1.

  15. Esme claims that two plants with RrYy always give 9 : 3 : 3 : 1, with simple dominance for both genes. Which reply has the correct reason?

    • No, because two genes followed together give 3 : 1
    • Yes, because the 16 boxes are the same for any two genes
    • Yes, because the dominant alleles stay together when passed on
    • No: the ratio needs the two genes to sort independently, as genes on different chromosomes do

  16. Model data

    32 plants from RrYy × RrYy. Found: 1 wrinkled green plant. Prediction: wrinkled green fills 1 box of 16, so 32 ÷ 16 = 2 plants are expected. Table: Claim card; columns item and plants; rows plants grown, boxes in the square, wrinkled green found, wrinkled green expected.

  17. Bo grows 32 plants from RrYy × RrYy (model data) and finds 1 wrinkled green plant. The claim is that the 1/16 prediction is wrong. Which reply is best?

    • The claim is weak: 2 are expected, and a count near 2 can happen by chance in a small group
    • The claim is right, because exactly 2 must appear
    • The claim is right, because the expected number is 8
    • The claim is weak, because 18 are expected

  18. Claim card: a test cross of RrYy with rryy shows the four allele combinations RrYy can pass on. Jun claims that a test cross of RrYy with rryy shows the four combinations RrYy can pass on. Which reason supports the claim?

    • The RY combination stays together, so only RY and ry offspring appear
    • The offspring come out 9 : 3 : 3 : 1, which shows the combinations
    • The rryy plant passes on its own gene pairs, rr and yy, so the offspring copy them
    • The rryy plant passes on only ry, so each offspring shows one combination from the other plant
PencilGopencilgo.com

9th grade Two-trait crosses with a 4 by 4 square worksheet – printable
Print: 123456

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.

More biology

See all Biology

Every sheet you scan goes into your child’s record: dated, marked and ready for the year-end portfolio. Homeschool records

Ready for easier practice?

Print a sheet, scan it when it’s done, and PencilGo picks the next one.

Create a free account