Blended and both-showing traits

Grade 9 Science Worksheet

Circle the best answer.

1. 1.

   Ari crosses two pink snapdragons. What is the ratio of red to pink to white flowers in the offspring?

   • 2 red : 1 pink : 1 white
   • 0 red : 4 pink : 0 white
   • 3 red : 0 pink : 1 white
   • 1 red : 2 pink : 1 white
2. 2.

   Bo crosses a pink snapdragon with a white one. What is the ratio of pink to white flowers in the offspring?

   • 4 pink : 0 white
   • 1 red : 1 white
   • 3 pink : 1 white
   • 1 pink : 1 white
3. 3.

   Esme crosses a roan parent with a red parent in a model cross. What is the ratio of red to roan calves?

   • 4 red : 0 roan
   • 3 red : 1 roan
   • 2 red : 1 roan
   • 1 red : 1 roan

4. Read this first

   Cross results for model flower K (model data)

   generation	what the plants showed
   parents	one violet-flowered line and one white-flowered line
   F1	100 violet
   F2	150 violet and 50 white

5. 4.

   Jun reads the cross results for model flower K. Which pattern fits?

   • Codominance: the F1 shows violet and white patches
   • Incomplete dominance: the F1 is a pale violet
   • Complete dominance: violet hides white in the F1
   • Blending: white is lost for good after the F1

6. Table

   Cross results for model cattle (model data), 3 rows. Columns: generation, what the calves showed. Row 1: parents, one red line and one white line. Row 2: F1, roan, with red hairs and white hairs. Row 3: F2, 26 red, 49 roan and 25 white.

7. 5.

   Kira reads the cross results for model cattle. Which pattern fits?

   • Complete dominance: red hides white in the F1
   • Codominance: roan calves show both hair colors
   • Incomplete dominance: roan is one in-between color
   • Blending: mixed coats cannot split into red and white again

8. Table

   Four traits and their heterozygote looks (model), 4 rows. Columns: trait, what the heterozygote shows. Row 1: pea seed shape, round seeds, as one allele hides the other. Row 2: snapdragon flower color, pink flowers, in between red and white. Row 3: roan cattle coat, red hairs and white hairs together. Row 4: ABO blood type AB, both the A form and the B form.

9. 6.

   Luz reads a card of four traits. Which row shows incomplete dominance?

   • Row 3: the roan cattle coat
   • Row 1: the pea seed shape
   • Row 4: ABO blood type AB
   • Row 2: snapdragon flowers
10. 7.

    Milo plans 200 seedlings from the cross in the square (model data). About how many should have red flowers?

    • About 150, three quarters of 200
    • About 0, since the red allele is blended away
    • About 50, one quarter of 200
    • About 100, the two pink boxes together
11. 8.

    Noah expects 120 calves from the cross in the square (model data). About how many should be roan?

    • About 120, since a roan parent passes on its roan look
    • About 90, three quarters of 120
    • About 60, half of 120
    • About 30, one quarter of 120

12. Genotype ratio and ratio of looks (model)

    cross	genotype ratio	ratio of looks
    pea Vv × Vv	1 : 2 : 1	3 : 1
    snapdragon RW × RW	1 : 2 : 1	1 : 2 : 1

13. 9.

    Tala reads a table of two crosses. Why does the snapdragon ratio of looks match its ratio of genotypes?

    • Red is dominant, so RR and RW look the same
    • Snapdragons have three alleles, one for each look
    • The alleles blend into one pink allele that is passed on
    • Each genotype has its own look, so 3 genotypes give 3 looks

14. Three patterns of dominance (model)

    pattern	heterozygote example	heterozygote look
    complete dominance	pea Vv	violet
    incomplete dominance	snapdragon RW	pink
    codominance	roan cattle RW	red hairs and white hairs

15. 10.

    Zee crosses two heterozygous parents in each pattern. What is true for all three patterns?

    • The heterozygote shows one mixed color
    • The ratio of looks is 3 : 1
    • The genotypes come out 1 : 2 : 1
    • The heterozygote hides one of its alleles