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

4. A cattle cross (model data)

   coat	calves counted
   red	24
   roan	51
   white	25

5. 3.

   Esme reads a model cattle cross card. The calves are red, roan and white. Which parents could these be?

   • One red parent and one white parent (RR × WW)
   • Two roan parents (RW × RW)
   • One roan parent and one white parent (RW × WW)
   • One roan parent and one red parent (RW × RR)
7. 4.

   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
   • 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
   • 3 in 4, since 3 of the 4 boxes are not white
8. 5.

   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 4.

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

9. Notebook

   Notes on two pink snapdragons (classmate's notebook), 4 lines. Columns: line, entry. Line 1: Each pink parent is RW and passes on one of its two alleles, chosen at random. Line 2: So the four boxes are RR, RW, RW and WW. Line 3: The genotypes are in the ratio 1 : 2 : 1. Line 4: The flower colors are in the ratio 3 : 1.

10. 6.

    Milo reads a classmate's notebook about two pink snapdragons. Which line has the mistake?

    • Line 2: the two RW boxes should be counted as one box
    • Line 4: the colors are 1 red : 2 pink : 1 white
    • Line 3: the genotypes should be in the ratio 3 : 1
    • Line 1: a pink parent should pass on both of its alleles

11. 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.

12. 7.

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

    • Line 1: a roan calf should show red hairs alone, since R is dominant
    • Line 3: each hair stays red or white and does not blend
    • Line 2: roan is incomplete dominance, with one in-between color
    • Line 4: two roan parents give roan calves, not red or white
13. 8.

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

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

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

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

15. 9.

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

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

16. 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.

17. 10.

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

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