Traits controlled by many genes, and their bell-shaped spread

Grade 9 Science Worksheet - Building Confidence

Circle the best answer.

1. 1.

   Ari reads a bar graph of bean seed masses. How many seeds have a mass of 430 mg?

   • 3 seeds
   • 22 seeds
   • 17 seeds
   • 9 seeds
2. 2.

   Bo reads a bar graph for a second lot of bean seeds. Which mass has the most seeds?

   • 530 mg
   • 24 seeds, the height of the tallest bar
   • 540 mg
   • 500 mg, the lightest class
4. 3.

   Jun reads the filled square for a model wheat cross, AaBb × AaBb. How many of the 16 boxes hold exactly 2 dark alleles?

   • 1 box, like a corner box
   • 4 boxes
   • 6 boxes
   • 8 boxes
5. 4.

   Kira reads the same square. How many of the 16 boxes hold exactly 4 dark alleles?

   Use the picture in question 3.

   • 16 boxes
   • 1 box
   • 4 boxes
   • 6 boxes
6. 5.

   Luz reads the same square again. How many of the 16 boxes hold exactly 1 dark allele?

   Use the picture in question 3.

   • 4 boxes
   • 6 boxes
   • 1 box, like the corner boxes
   • 2 boxes, one for each genotype

7. Read this first

   Wheat kernel color, 64 equally likely offspring (model data)

   dark alleles	offspring
   0	1
   1	6
   2	15
   3	?
   4	15
   5	6
   6	1

8. 6.

   Noah reads a count table for a model wheat cross with 3 genes. What number goes in the blank?

   • 1 offspring
   • 30 offspring
   • 15 offspring
   • 20 offspring
9. 7.

   Pia reads a second count table for the model wheat cross with 3 genes. What number goes in the blank?

   • 6 offspring
   • 20 offspring
   • 1 offspring
   • 15 offspring

10. Trait card (model data)

    trait	genes	kernel colors
    wheat kernel color	3	7

11. 8.

    Ren reads a trait card for wheat kernel color. Which choice explains why this trait is called polygenic?

    • The soil alone decides the kernel color
    • Three genes each add to the kernel color
    • The kernel color blends two parents' colors
    • One gene alone sets the kernel color
12. 9.

    Tala reads a trait card for bean seed mass. Which choice names this kind of variation?

    • Soil variation: the soil alone sets the mass
    • Discontinuous variation: two or very few clear groups
    • Blended variation: offspring mix the traits of two parents
    • Continuous variation: many small steps with no clear groups

13. Use this

    Counts of offspring by dark alleles (model data). Columns: dark alleles | table P (of 4) | table Q (of 16). Row 1: 0 | 1 | 1. Row 2: 1 | 2 | 4. Row 3: 2 | 1 | 6. Row 4: 3 | - | 4. Row 5: 4 | - | 1.

14. 10.

    Zee compares two count tables. One comes from a cross with 1 gene and one from a cross with 2 genes. Which choice names the 2-gene table?

    • Table Q, since 16 offspring means 16 classes
    • Table P, since 3 classes are enough for 2 genes
    • Table P, since a trait is controlled by one gene
    • Table Q, since 5 classes need 2 genes