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

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

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

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

   • Complete dominance: violet hides white in the F1
   • Incomplete dominance: the F1 is a pale violet
   • Blending: white is lost for good after the F1
   • Codominance: the F1 shows violet and white patches
6. 5.

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

   • About 0, since the red allele is blended away
   • About 150, three quarters of 200
   • About 50, one quarter of 200
   • About 100, the two pink boxes together
7. 6.

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

   • About 30, one quarter of 120
   • About 60, half of 120
   • About 90, three quarters of 120
   • About 120, since a roan parent passes on its roan look
8. 7.

   Pia expects about 90 pink seedlings from the cross in the square (model data). About how many seedlings is that in all?

   • About 180, since pink is half
   • About 360, since pink is one quarter
   • About 270, since 90 is multiplied by 3
   • About 120, since pink is three quarters

9. Table

   Two crosses of heterozygous parents (model), 2 rows. Columns: cross, the four boxes, the four looks. Row 1: pea Vv × Vv, VV, Vv, Vv and vv, violet, violet, violet and white. Row 2: snapdragon RW × RW, RR, RW, RW and WW, red, pink, pink and white.

10. 8.

    Ren compares two crosses of heterozygous parents. How do the ratios of looks compare?

    • Pea 1 : 2 : 1; snapdragon 1 : 2 : 1, since both have the same boxes
    • Pea 1 violet : 2 mixed : 1 white; snapdragon 3 : 1
    • Pea 3 : 1; snapdragon 3 : 1, since both crosses use two heterozygous parents
    • Pea 3 violet : 1 white; snapdragon 1 red : 2 pink : 1 white

11. 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

12. 9.

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

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

13. 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

14. 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 heterozygote hides one of its alleles
    • The genotypes come out 1 : 2 : 1