Two-trait crosses with a 4 by 4 square

Grade 9 Science Worksheet

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. 1.

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

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. 2.

   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?

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

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. 3.

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

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

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

   • 3 : 1
   • 1 : 1 : 1 : 1
   • 1 : 3 : 3 : 9
   • 9 : 3 : 3 : 1
9. 5.

   Milo reads the same filled square but looks at seed shape alone. What is the ratio of round seeds to wrinkled seeds?

   Use the picture in question 4.

   • 9 : 7
   • 3 : 1
   • 9 : 1
   • 1 : 1

10. 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.

11. 6.

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

    • 3/4, the chance for one trait
    • 3/2
    • 3/16, the chance for one dominant trait and one recessive
    • 9/16
12. 7.

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

    • 1/9, from the 9 in the ratio
    • 1/16
    • 1/4, the chance for one trait
    • 1/2
13. 8.

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

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

14. 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.

15. 9.

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

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

16. 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.

17. 10.

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

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