Blended and both-showing traits

Grade 9 Science Worksheet - Challenge Me

Circle the best answer.

1. Read this first

   A snapdragon cross (model data)

   offspring counted	flower color
   60	all pink

2. 1.

   Ari reads a snapdragon cross card. Every offspring has pink flowers. Which parents could these be?

   • One pink parent and one white parent (RW × WW)
   • Two pink parents (RW × RW)
   • One red parent and one white parent (RR × WW)
   • One red parent and one pink parent (RR × RW)
3. 2.

   Bo reads a snapdragon cross card. The offspring are about half pink and half white. Which parents could these be?

   • One red parent and one white parent (RR × WW)
   • Two pink parents (RW × RW)
   • One red parent and one pink parent (RR × RW)
   • A pink parent and a white parent (RW × WW)
5. 3.

   Jun picks one seedling at random from the pink × pink offspring. Its flowers are not white. What is the chance they are pink?

   • 1 in 2, since 2 of the 4 boxes are pink
   • 3 in 4, since 3 of the 4 boxes are not white
   • 1 in 3, since 1 of the 3 boxes that are not white is pink
   • 2 in 3, since 2 of the 3 non-white boxes are pink
6. 4.

   Kira grows two seedlings from the cross of two pink snapdragons. What is the chance that both have white flowers?

   Use the picture in question 3.

   • 1 in 16, since 1/4 × 1/4
   • 1 in 4, the chance for one seedling
   • 0, since the white allele is blended away in pink plants
   • 1 in 2, since 1/4 + 1/4
7. 5.

   Luz follows a model cross of a roan parent and a red parent. What is the chance that three calves in a row are roan?

   • 1 in 6, since 1/2 ÷ 3
   • 1 in 4, since 1/2 × 1/2
   • 1 in 8, since 1/2 × 1/2 × 1/2
   • 1 in 2, the chance for one calf

8. Notebook

   Notes on a roan calf (classmate's notebook), 4 lines. Columns: line, entry. Line 1: A roan calf has one red allele and one white allele (RW). Line 2: Both alleles show, so red hairs and white hairs grow side by side. Line 3: The red and white hairs blend into one pink color on every hair. Line 4: Two roan parents can give red, roan and white calves.

9. 6.

   Noah reads a classmate's notebook about a roan calf in a model cross. Which line has the mistake?

   • Line 4: two roan parents give roan calves, not red or white
   • Line 3: each hair stays red or white and does not blend
   • Line 1: a roan calf should show red hairs alone, since R is dominant
   • Line 2: roan is incomplete dominance, with one in-between color

10. Notebook

    Notes on a pink × pink cross (classmate's notebook), 4 lines. Columns: line, entry. Line 1: The expected ratio is 1 red : 2 pink : 1 white. Line 2: Of 80 seedlings, the expected counts are 20 red, 40 pink and 20 white. Line 3: The class counted 23 red, 38 pink and 19 white. Line 4: The counts are not 20, 40 and 20, so the cross does not follow the ratio.

11. 7.

    Pia reads a classmate's notebook about a pink × pink cross. Which line has the mistake?

    • Line 2: 80 seedlings should give counts that add to 100
    • Line 1: the expected ratio should be 3 : 1
    • Line 3: the class should have counted exactly 20, 40 and 20
    • Line 4: counts land near the expected counts, not on them
12. 8.

    Ren says pink snapdragons breed true, so two pink parents give only pink offspring. Do you agree?

    • No, because two pink parents give 3 pink to 1 white
    • Yes, because pink parents have no other alleles to pass on
    • No, because pink parents also give red and white offspring
    • Yes, because red and white blend into one pink allele

13. Class counts for a pink × pink cross (model data)

    flower color	counted	expected
    red	24	25
    pink	52	50
    white	24	25

14. 9.

    Tala says the cross failed because the counts are not exactly the expected counts. Do you agree?

    • Yes, because counts must match the ratio exactly
    • No, because 52 pink shows pink is dominant over red and white
    • No, because real counts land near the ratio, not on it
    • Yes, because the cross should give 75 colored and 25 white

15. Table

    Two patterns (model), 2 rows. Columns: pattern, what the heterozygote shows. Row 1: incomplete dominance, one in-between look, such as pink snapdragons. Row 2: codominance, both parent looks side by side, such as roan red and white hairs.

16. 10.

    Zee says roan is just incomplete dominance, since the roan calf looks in between red and white. Do you agree?

    • Yes, because both patterns give one mixed color
    • No, because roan shows both looks, not one in-between look
    • No, because roan parents give roan calves, not red or white
    • No, because roan is complete dominance, with red hiding white