Traits controlled by many genes, and their bell-shaped spread
Grade 9 Science Worksheet - Challenge Me
Circle the best answer.
Read this first
Trait cards: X is Mendel's pea counts, Y is model data
trait classes seen counts X: pea flower color 2 705 and 224 Y: rice plant height 7 2, 9, 21, 31, 23, 11, 3 Tala reads two trait cards. Which pairing fits the cards best?
- X fits many genes with a smooth spread; Y fits one gene with two clear groups
- X fits one gene with two clear groups; Y fits many genes with a smooth spread
- Both fit one gene, since each trait is controlled by a single gene
- X fits one gene; Y shows the parents' heights blending into a bell
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 Jun compares two model traits that both peak in the middle. Which trait probably has more genes, and why?
- Trait Q, since 38 is the largest count in the tables
- Neither, since both traits peak in the middle and have one gene
- Trait P, since fewer and bigger steps point to more genes
- Trait Q, since 5 finer classes point to more genes
Classes in a model trait with additive alleles
classes dark alleles 9 0 to 8 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?
- 9 genes, one gene for each class
- 4 genes
- 5 genes, since half of 9 rounds up
- 8 genes, one gene for each dark allele
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 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?
- 20 cm from the soil and 20 cm from the seed lot
- 40 cm from the soil, since it changed the alleles
- 30 cm from the soil and 10 cm from the seed lot
- 40 cm from the seed lot, since genes set height
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 110 cm, since the seeds keep the soil's boost
- About 100 cm, halfway between the two soils
- About 90 cm, the lot P poor-soil value
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 Noah's notebook is about one AaBb × AaBb cross. One line is wrong. Which fix is right?
- Line 3 should say the counts add to 16 offspring
- Line 4 should say the class with 2 dark alleles is the rarest
- Line 2 should have 3 classes, since one gene sets the trait
- Line 1 should say a parent passes on a blend of its two alleles
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 Pia's notebook is about one oat seed lot grown in two soils. One line is wrong. Which fix is right?
- Line 3 should say the gap is 225 cm, from adding the two means
- Line 2 should give a range, not a mean, for each soil
- Line 1 should say each soil had its own seed lot, since genes alone set height
- Line 4 should say the soil changed how tall the plants grew, not the alleles
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 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
Ren reads a histogram of height for a whole model group. Which reply gives the best reason for the bell shape?
- The bell shows the parents' heights blending into one middle height
- Many genes plus surroundings influence height, so a smooth bell is expected
- One gene sets height, so the group would split into two clear groups
- Many genes set height by themselves, so surroundings play no part
Claim card (model data)
claim trait soil effect height is not polygenic if soil changes it plant height rich soil raises the mean by 20 cm Bo claims that if rich soil raises plant height, then height cannot be polygenic. Which reply is best?
- No: many polygenic traits are also influenced by surroundings, so soil can shift the bell
- No: the soil changes the genes, and that makes height polygenic
- Yes: a polygenic trait has two classes, which soil would blur
- Yes: polygenic traits are set by genes alone, so soil could not shift the bell