Mendel's laws of segregation and independent assortment

Grade 9 Science Worksheet

Circle the best answer.

1. 1.

   Ari fills the square for two Vv pea plants and counts the genotypes. What is the genotype ratio?

   • 1 : 1 : 1
   • 1 : 2 : 1
   • 3 : 1
   • 2 : 1 : 1
2. 2.

   Bo crosses two Tt pea plants. What is the ratio of tall plants to dwarf plants in the offspring?

   • 1 tall : 3 dwarf
   • 3 tall : 1 dwarf
   • 1 tall : 1 dwarf
   • 1 tall : 2 mixed : 1 dwarf
3. 3.

   Esme crosses two Yy pea plants. What is the chance that one offspring seed is green?

   • 1 in 4, since only yy is green
   • 3 in 4
   • 1 in 2, since a y makes a seed green
   • 1 in 3, since there are three kinds of seed
4. 4.

   Model data: Jun's class plants 400 seeds from Rr × Rr parents. About how many seeds are expected to be round?

   • 200 seeds
   • 300 seeds
   • 75 seeds
   • 100 seeds
5. 5.

   Model data: Kira's class plants 120 seeds from Yy × Yy parents. About how many seeds are expected to be Yy, with one yellow and one green allele?

   • 30 seeds
   • 90 seeds
   • 40 seeds
   • 60 seeds

6. Read this first

   Two genes on different chromosomes (model)

   gene	each parent's alleles	where the gene sits
   seed color	Yy	one chromosome
   seed shape	Rr	a different chromosome

7. 6.

   Model data: Luz's class plants 320 seeds from YyRr × YyRr parents. About how many seeds are expected to be yellow, whatever their shape?

   • 160 seeds
   • 240 seeds
   • 180 seeds
   • 80 seeds

8. Test cross card

   A test cross (model data), 1 row. Columns: plant crossed with a white-flowered vv plant, offspring. Row 1: violet-flowered plant, letters unknown, 24 violet and 26 white.

9. 7.

   Milo reads a test cross card. What are the letters of the violet-flowered plant, most likely?

   • VV (two violet alleles), since the plant is violet
   • vv (two white alleles), since white offspring appeared
   • Not known, since 24 and 26 are not exactly 1 : 1
   • Vv (one violet, one white allele), since about half are white

10. Mendel's real counts, plant height (real data: Mendel)

    generation	tall plants	dwarf plants
    F2	787	277

11. 8.

    Ren divides Mendel's F2 plant-height counts. About what is the ratio of tall plants to dwarf plants?

    • About 3.84 : 1
    • About 2.84 : 1, close to 3 : 1
    • About 0.35 : 1
    • About 2.84 : 1, which does not fit 3 : 1

12. Mendel's real counts, seed shape (real data: Mendel)

    generation	round seeds	wrinkled seeds	seeds in all
    F2	5,474	1,850	7,324

13. 9.

    Tala wants the count that a 3 : 1 ratio predicts. How many round seeds does 3/4 of the total give?

    • 5,493 seeds, close to Mendel's count
    • 1,831 seeds
    • 5,474 seeds, since the prediction must equal the count
    • 2,441 seeds

14. Mendel's real F2 counts (real data: Mendel)

    characteristic	plants with the dominant trait	plants with the recessive trait
    flower color	705	224
    plant height	787	277
    seed color	6,022	2,001

15. 10.

    Zee divides each row of Mendel's F2 counts. Which characteristic has a ratio closest to 3 : 1?

    • Plant height, about 2.84 : 1
    • Seed color, about 3.01 : 1
    • Flower color, about 3.15 : 1
    • Each of them, since each ratio is exactly 3 : 1