Worksheet

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
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Two-trait crosses with a 4 by 4 square

Answer Key - Grade 9 Science Worksheet - Challenge Me

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