Worksheet

Sweet Peas, Soup Peas and a Leaf Mold

Grade 8 gene mutation practice: pea seed data, a planting test and a leaf-mold trial show changed proteins with harmful, helpful or neutral effects.

Grade 8ScienceInteractive · Printable

Aligned toMS-LS3-1

Play online Play as a game

PrintLetter-size worksheet Answer keyPrintable answers

Assign to classAssign to your classes, or get a join code

What’s included

Single worksheet
Auto-graded online
1 NGSS standard
Printable answer key
11 questions
Classroom-ready

Details

Format: Interactive · Printable
Grade: Grade 8
Subject: Science
Question types: Fill in the blank, Multiple choice, Circle the answer, Short answer

About this worksheet

What students practice

Students explain how a changed enzyme in pea seeds leads to more sugar and wrinkled seeds.
Students use planting and leaf-mold data to decide when a mutation is harmful, helpful or neutral.
Students argue from evidence about whether a mutation helps the organism that carries it.

How to use

Read paragraphs 1 to 3 with Table 1 first and trace gene, protein and trait aloud, then let students work through Part 2 on their own.

Curriculum

NGSS standard covered

MS-LS3-1

Explain how gene mutations can change proteins and have harmful, helpful or neutral effects on an organism.

Preview

OwlSheets.com

Name Date

Sweet Peas, Soup Peas and a Leaf Mold

Follow two pea gene changes from protein to trait.

Part 1: Round seeds and wrinkled seeds

Read the passage and Table 1, then answer questions 1 to 4.

A Field Day at Hollow Creek Farm

1Every June, the farm-to-school program at Alder Point Middle School visits Hollow Creek Farm, which grows the peas served in the school cafeteria. This year eighth grader Sora Whitfield asked the farmer, Mr. Tavita Ngata, why he grows two kinds of peas. One kind has smooth, round dry seeds that cooks use for split pea soup. The other has wrinkled dry seeds, and its green peas are sold fresh or frozen because they taste sweet. Mr. Ngata explained that the two kinds differ mainly in one gene.

2A gene is a section of DNA that carries the instructions for building a protein. In a growing pea seed, sugar arrives from the leaves, and the seed links much of it together into starch. A protein called the branching enzyme helps the seed build starch. In wrinkled peas, the gene for the branching enzyme has a mutation, a change in its DNA, and the enzyme the seed builds from it does not work. A lab that tests seeds for the farm also found a pea line with a different change in the same gene. Mr. Ngata calls it line N.

3Sugar dissolved in a seed draws water into it. Near the end of the season, the seeds dry out in the pods, and they shrink as their water leaves. Table 1 shows the lab's results for the three kinds of seeds.

4The farm also tests how well seeds sprout. Each spring, Mr. Ngata plants 100 seeds of each kind in early April, when the soil is cold and wet, and 100 more in late May, when the soil is warm. Seeds take longer to sprout in cold soil, and molds in the soil that rot seeds grow well on sugar leaking out of a seed.

5A second gene matters later in the summer. Powdery mildew is a mold that can coat pea leaves in white powder, and badly coated plants make fewer pods. To get inside a leaf cell, the mildew needs a working MLO protein, which pea leaf cells normally make. Some pea lines have a mutation in the MLO gene, so they make no working MLO protein. Mr. Ngata grew both kinds of plants side by side in a damp year when mildew spread and in a dry year when it did not.

Table 1: Pea Seeds Tested by the Lab (averages)
Seed kind	Branching enzyme	Starch (% dry mass)	Sugar (% dry mass)	Water, growing seed (%)	Dry seed shape
Round	Works	60	5	55	Smooth, round
Wrinkled	Does not work	33	10	70	Wrinkled
Line N	Works	60	5	55	Smooth, round

Use Table 1. Compare the starch in round seeds and wrinkled seeds.

Wrinkled seeds have percentage points less starch than round seeds.

Use paragraph 2 and Table 1. Why do wrinkled seeds hold about twice as much sugar as round seeds?

A. Without a working branching enzyme, less of the arriving sugar becomes starch.
B. The changed gene is made of sugar, so the seed stores the extra sugar from it.
C. The seed's roots pull extra sugar out of the soil to make up for the mutation.
D. The wrinkles in the seed coat let more sugar from the leaves slip inside.

Use paragraph 3 and Table 1. Which explanation of the wrinkled shape fits the evidence best?

A. The extra starch made the growing seed heavy, so it folded under its own weight.
B. The changed gene wrinkled the seed coat directly, the way a hand crumples paper.
C. More sugar drew more water into the growing seed, so it shrank more as it dried.
D. The seed held less water while growing, so its coat was already folded before drying.

Circle the two results that are evidence that the change in line N's gene has no effect on its seeds.

Wrinkled seeds: 10% sugarLine N seeds: 60% starch, the same as round seedsRound seeds: 55% water while growingLine N seeds: smooth and round when dry, like round seedsWrinkled seeds: 33% starch

Part 2: In the field

Use Tables 2 and 3 and paragraphs 4 and 5 to answer questions 5 to 11.

Table 2: Seedlings Up After 3 Weeks (100 seeds of each kind)
Seed kind	Cold, wet soil (April)	Warm soil (May)
Round	86	94
Wrinkled	58	92
Line N	85	95

Table 3: Mildew Trial in a Damp Year and a Dry Year (averages per plant)
MLO protein	Damp: leaf coated (%)	Damp: pods	Dry: leaf coated (%)	Dry: pods
Works (typical)	40	14	0	22
None (mutation)	2	21	0	22

Use Table 2. Compare the round and wrinkled seeds planted in April.

In cold, wet soil, fewer wrinkled seeds than round seeds came up.

Which conclusion do Table 2 and paragraph 4 support best?

A. Cold soil lowers sprouting by about 10 seeds for each of the three kinds.
B. The mutation lowers sprouting in cold, wet soil but not much in warm soil.
C. The mutation lowers sprouting in warm soil but raises it in cold, wet soil.
D. Line N seeds sprout far worse than round seeds in both kinds of soil.

Use Table 3. Compare the pods on the two kinds of plants in the damp year.

Plants with the MLO mutation made more pods per plant than typical plants.

Use paragraph 5 and Table 3. Why were the leaves of plants with the MLO mutation almost free of mildew in the damp year?

A. Without a working MLO protein, the mold could rarely get into their leaf cells.
B. Their leaves made extra MLO protein, which coated the leaves and washed the mold off.
C. The mutation made the plants grow more pods, and the pods pulled the mold off the leaves.
D. The typical plants grew in a wetter part of the field, so the mold reached them first.

In the dry year, both kinds of plants made 22 pods. What does this result suggest about the MLO mutation?

A. It helps the plants make more pods in a dry year than typical plants make.
B. It harms the plants in dry years, when they make fewer pods than in damp years.
C. It disappears from the plants' DNA in dry years and comes back in damp years.
D. It helped when mildew spread but made little difference when it did not.

10.

Use Tables 2 and 3. Fill in each blank with a word from the word bank. A word may be used more than once.

Word bank: harmful · helpful · neutral

Compared with round seeds, the wrinkled-seed mutation is for sprouting in cold, wet soil. The change in line N is for sprouting in both soils. In the damp year, the MLO mutation is . In the dry year, the MLO mutation is .

11.

Sora's classmate says, "The wrinkled-seed mutation is helpful to the pea plant, because it makes the peas sweet." Do you agree? Write a claim, give evidence from Tables 1 and 2, and explain your reasoning from the gene to the protein to the trait to the effect on the plant.