Mendel's laws of segregation and independent assortment

Grade 9 Science Worksheet - Challenge Me

Circle the best answer.

1. 1.

   Ari picks one violet-flowered offspring of two Vv plants at random. What is the chance that it is Vv?

   • 3 in 4, since 3 of the 4 boxes are violet
   • 1 in 2, since 2 of the 4 boxes are Vv
   • 1 in 3, since 1 of the 3 violet boxes is a Vv plant
   • 2 in 3, since 2 of the 3 violet boxes are Vv
2. 2.

   Bo crosses a round plant with a wrinkled plant (rr). If the round plant is Rr, what is the chance that three offspring in a row are all round?

   • 1 in 8
   • 3 in 4
   • 1 in 4
   • 1 in 2

3. Read this first

   Two genes on different chromosomes (model)

   gene	each parent's alleles	where the gene sits
   flower position	Aa	one chromosome
   pod color	Gg	a different chromosome

4. 3.

   Esme crosses two AaGg plants (A for axial flowers, a for terminal; G for green pods, g for yellow). What is the chance one offspring has terminal flowers and yellow pods?

   • 9 in 16
   • 1 in 16
   • 1 in 4
   • 1 in 2, since 1/4 + 1/4

5. Mendel's real counts, flower position (real data: Mendel)

   generation	what the plants showed
   F1	100 percent axial
   F2	651 axial and 207 terminal

6. 4.

   The F2 plants came from F1 plants crossed with themselves (A for axial flowers, a for terminal). Jun works backward. What were the letters of the F1 plants?

   • Half Aa and half AA, since the F2 is not exactly 3 : 1
   • AA (two axial alleles), since the terminal allele disappeared in the F1
   • aa (two terminal alleles), since terminal flowers appeared
   • Aa (one axial, one terminal allele), since the F2 is near 3 : 1

7. Cross card

   A cross of two tall plants (model data), 1 row. Columns: parents, offspring. Row 1: two tall plants, letters unknown, 30 tall and 10 dwarf.

8. 5.

   Kira reads a cross card for two tall pea plants. What are the parents' letters, most likely?

   • TT × TT (both parents have two tall alleles)
   • TT × Tt (one parent has two tall alleles)
   • Tt × Tt (each parent has one tall, one dwarf allele)
   • Tt × tt (one parent has two dwarf alleles)

9. Notebook

   Notes on two Vv plants (classmate's notebook), 4 lines. Columns: line, entry. Line 1: Each Vv parent passes on one of its two alleles, chosen at random. Line 2: So the four boxes are VV, Vv, Vv and vv. Line 3: The three kinds of genotype are in the ratio 3 : 1. Line 4: The phenotypes are 3 violet to 1 white.

10. 6.

    Milo reads a classmate's notebook about two Vv pea plants. Which line has the mistake?

    • Line 3: the genotypes are in the ratio 1 : 2 : 1
    • Line 2: the two Vv boxes should be counted as one
    • Line 1: a parent should pass on both of its alleles
    • Line 4: the phenotypes are in the ratio 1 : 2 : 1

11. Notebook

    Notes on a class seed count (classmate's notebook), 4 lines. Columns: line, entry. Line 1: A class crossed Rr × Rr and planted 400 seeds (model data). Line 2: A 3 : 1 ratio predicts 300 round and 100 wrinkled. Line 3: The class counted 293 round and 107 wrinkled. Line 4: These are not exactly 300 and 100, so the 3 : 1 idea is wrong.

12. 7.

    Pia reads a classmate's notebook about a class seed count. Which line has the mistake?

    • Line 4: counts near 300 and 100 still fit 3 : 1
    • Line 3: the class should have counted exactly 300 round
    • Line 1: Rr × Rr cannot give wrinkled seeds
    • Line 2: a 3 : 1 ratio predicts 100 round and 300 wrinkled
13. 8.

    Ren says: two Vv parents with four offspring will have exactly 3 violet and 1 white. Do you agree?

    • No, because the ratio of looks is 1 : 2 : 1, not 3 : 1
    • Yes, because a 3 : 1 ratio fixes the numbers in a family of four
    • No, because each offspring has a 3 in 4 chance of violet, so four can differ
    • Yes, because the square has 3 violet boxes and 1 white box

14. Mendel's real counts, flower color (real data: Mendel)

    generation	what the plants showed
    F1	100 percent violet
    F2	705 violet and 224 white

15. 9.

    Tala claims that the F1 plants lost the white allele. Do you agree?

    • Yes, because 705 : 224 is not exactly 3 : 1
    • No, because the F1 flowers were pale violet, a blend
    • No, because 224 white F2 plants show the allele was still there
    • Yes, because 100 percent of the F1 plants had violet flowers
16. 10.

    Two Vv parents have three violet offspring so far. Zee says the next one must be white to make 3 : 1. Do you agree?

    • Yes, because the square has one white box left
    • No, because the next offspring is Vv, which blends violet and white
    • Yes, because a family has to match the 3 : 1 ratio
    • No, because the next offspring is violet with chance 3 in 4, as before