9th grade Traits controlled by many genes, and their bell-shaped spread worksheet

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

Grade 9 Science Worksheet - Challenge Me

Circle the best answer.

1. Read this first

   Counts of 100 offspring in two model traits

   class	trait P	trait Q
   1	25	6
   2	50	25
   3	25	38
   4	-	25
   5	-	6

2. 1.

   Jun compares two model traits that both peak in the middle. Which trait probably has more genes, and why?

   • Neither, since both traits peak in the middle and have one gene
   • Trait Q, since 38 is the largest count in the tables
   • Trait P, since fewer and bigger steps point to more genes
   • Trait Q, since 5 finer classes point to more genes

3. Classes in a model trait with additive alleles

   classes	dark alleles
   9	0 to 8

4. 2.

   Milo learns that a model trait has 9 classes, from 0 to 8 dark alleles. How many genes with two alleles each add up in this model?

   • 5 genes, since half of 9 rounds up
   • 8 genes, one gene for each dark allele
   • 4 genes
   • 9 genes, one gene for each class

5. Mean wheat plant height by seed lot and soil (model data)

   seed lot	poor soil (cm)	rich soil (cm)
   lot P	90	110
   lot Q	110	130

6. 3.

   Zee compares lot P in poor soil with lot Q in rich soil, a gap of 40 cm. How is the gap shared between soil and seed lot?

   • 30 cm from the soil and 10 cm from the seed lot
   • 40 cm from the seed lot, since genes set height
   • 40 cm from the soil, since it changed the alleles
   • 20 cm from the soil and 20 cm from the seed lot

7. Mean barley plant height by seed lot and soil (model data)

   seed lot	poor soil (cm)	rich soil (cm)
   lot R	60	85
   lot S	80	?

8. 4.

   Kira assumes rich soil adds the same height to each lot. What should the blank be for lot S in rich soil?

   • 85 cm, the lot R value
   • 130 cm, since the soil gain counts twice
   • 80 cm, since soil does not matter
   • 105 cm

9. Mean wheat plant height by seed lot and soil (model data)

   seed lot	poor soil (cm)	rich soil (cm)
   lot P	90	110
   lot Q	110	130

10. 5.

    Ari plants seeds saved from lot P plants that grew in rich soil, and grows them in poor soil. What mean height does the table predict?

    • About 70 cm, since poor soil lowers the lot a second time
    • About 90 cm, the lot P poor-soil value
    • About 100 cm, halfway between the two soils
    • About 110 cm, since the seeds keep the soil's boost

11. Notebook for AaBb × AaBb (model data)

    line	what the notebook says
    1	Each parent passes on one allele for each gene, chosen at random
    2	The counts for 0, 1, 2, 3 and 4 dark alleles are 1, 4, 6, 4 and 1
    3	These counts add to 15 offspring
    4	The class with 2 dark alleles is the most common

12. 6.

    Noah's notebook is about one AaBb × AaBb cross. One line is wrong. Which fix is right?

    • Line 4 should say the class with 2 dark alleles is the rarest
    • Line 3 should say the counts add to 16 offspring
    • Line 1 should say a parent passes on a blend of its two alleles
    • Line 2 should have 3 classes, since one gene sets the trait

13. Notebook for one oat seed lot in two soils (model data)

    line	what the notebook says
    1	One seed lot was grown in a poor soil and in a rich soil
    2	The mean height was 100 cm in poor soil and 125 cm in rich soil
    3	The 25 cm gap comes from the soil
    4	So the rich soil changed the alleles in the seeds

14. 7.

    Pia's notebook is about one oat seed lot grown in two soils. One line is wrong. Which fix is right?

    • Line 1 should say each soil had its own seed lot, since genes alone set height
    • Line 2 should give a range, not a mean, for each soil
    • Line 4 should say the soil changed how tall the plants grew, not the alleles
    • Line 3 should say the gap is 225 cm, from adding the two means

15. Notebook for AaBbCc × AaBbCc (model data)

    line	what the notebook says
    1	The model has 3 genes with additive alleles
    2	That gives 0 to 6 dark alleles, so 6 classes
    3	The counts are 1, 6, 15, 20, 15, 6 and 1 out of 64
    4	More genes give a smoother bell shape

16. 8.

    Esme's notebook is about one AaBbCc × AaBbCc cross. One line is wrong. Which fix is right?

    • Line 1 should say 6 genes, one for each dark allele
    • Line 3 should read out of 7, the number of classes
    • Line 2 should say 7 classes, since 0 to 6 is seven values
    • Line 4 should say more genes give fewer classes
17. 9.

    Ren reads a histogram of height for a whole model group. Which reply gives the best reason for the bell shape?

    • Many genes set height by themselves, so surroundings play no part
    • One gene sets height, so the group would split into two clear groups
    • The bell shows the parents' heights blending into one middle height
    • Many genes plus surroundings influence height, so a smooth bell is expected
18. 10.

    Luz claims that a bell shape means offspring blend the parents' traits. Both parents here have 2 dark alleles. Which reply is best?

    • No: 1 of 16 offspring has 0 dark alleles, fewer than either parent
    • No: each class has the same count, so nothing could blend
    • Yes: the most common class has 2 dark alleles, like the parents, so alleles blend
    • No: the middle class is the rarest, so nothing could blend