National Agricultural Literacy Curriculum Matrix

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Apple Genetics: The Phenomena of Different and the Same

Grade Level(s)

6 - 8

Estimated Time

60 minutes

Purpose

Using the context of apples, students will apply their knowledge of heredity and genetics to understand how both sexual and asexual plant propagation methods are used to develop new apple varieties as well as produce a uniform crop of apples for consumption. 

Materials

Activity 1:

  • Apple Genetics PowerPoint
  • Apple Genetics worksheet, 1 per student
  • Per group of students:
    • 1 Paper Plate
    • 1 Whole Braeburn Apple 
    • 1 Whole Royal Gala Apple
    • 1 Whole Jazz Apple
    • 1 Knife (or apple slicer to cut apple)

Activity 2:

Essential Files (maps, charts, pictures, or documents)

Vocabulary

Punnet Square: a diagram used to predict an outcome of a particular cross or breeding experiment

allele: a variant of a gene

dominant allele: an allele whose trait always shows up in the organism when the allele is present (written as uppercase letter)

gene: a section of DNA that codes for a certain trait

genotype: an organism's genetic makeup or allele combinations

heredity: the passing of traits from parents to offspring

heterozygous: having 2 different alleles for a trait.

homozygous: having two identical alleles for a trait.

phenotype: an organism's physical appearance or visible trait

probability: a number that describes how likely it is that an event will occur

recessive allele: an allele that is masked when a dominant allele is present (written as lower case letter)

trait: a characteristic that an organism can pass on to its offspring through its genes

Did you know? (Ag Facts)

  • Apples are a member of the rose family.1
  • More than 2,500 varieties of apples are grown in the United States, but only the crabapple is native to North America.1
  • The average person eats 65 apples per year.1
  • Apples are 25% air, which is why they float in water.1

Background Agricultural Connections

This lesson can be nested into a storyline as an episode exploring phenomenon that can be observed in apples. In this episode, students investigate the question, "What makes apple varieties different?" Phenomena-based lessons include storylines which emerge based upon student questions. Other lesson plans in the National Agricultural Literacy Curriculum Matrix may be used as episodes to investigate student questions needing science-based explanations. For more information about phenomena storylines visit nextgenstorylines.org.


Prior to this lesson, students should know that all cells of an organism have DNA. DNA is the blueprint providing the organism with coded instructions for proper function and development.  Students should understand that genes are sections of DNA that are responsible for passing specific traits from parent to offspring. Students will need to be familiar with vocabulary such as phenotype, genotype, homozygous, and heterozygous to successfully complete the lesson and student worksheet and determine probabilities associated with possible offspring using a Punnett Square.  Students will be introduced to several varieties of apples and discover how new varieties can be created through crossbreeding. 

Key STEM Ideas

Genetics is the study of heredity, while heredity is the passing of traits from parents to offspring. This lesson will help solidify key genetics vocabulary words. 

The main idea of this lesson is to show the application of genetic crossing for the benefit of agriculture by producing apples with a variety of traits.

Gregor Mendel was a priest who worked with the genetic crossing of pea plants.  He would cross purebred short pea plants with purebred tall pea plants.  Through his experiments he determined that some traits were visible in the plant (dominant traits) while others were not, but were still able to be passed on to future generations (recessive traits). Understanding what we see and what the genetic makeup of an organism is can be quite different.  When you look at an organism, its physical characteristics are all dependent on a specific allele combination.  This is the difference between phenotype and genotype.  Students will use Punnett Squares in this lesson to help determine all the possible allele combinations in a genetic cross and their probabilities. 

Crossbreeding allows breeders to create better quality apples by incorporating traits from two parent plants into the seeds of a new generation of plants.  Breeders must understand both genotypes and phenotypes to accomplish this task.  Breeders must also decide which traits are desirable and should be selected.  This is an intensive process that involves breeding successive generations of apples with the preferred traits in order to get the final product. 

Connections to Agriculture

Apples are an important agricultural crop. There are about 7,500 apple producers in the United States.  Washington, New York, and Michigan are the leaders in apple production. Growers produce a variety of different kinds of apples.  Some apples are used for baking while others are used for eating. Apples are a good snack choice as they contain no fat and relatively few calories while being high in fiber and vitamin C. 

Apples are grown through a process called grafting rather than being grown from seed. This is done because most apple varieties are self-unfruitful, which means their blossoms must be fertilized with the pollen of a separate variety in order to produce fruit. The fruit has traits from the parent tree, but the seeds inside will be a cross of the two varieties. This mixture of genetic material in the seeds means the grower won’t know what traits a tree grown from these seeds will have and what the resulting fruit will taste like.

To avoid this uncertainty apple growers do not grow new trees from seed. Instead, new apple trees are propagated through a process called grafting. In this process a special cut is made into the rootstock of a tree. Then, they graft or transplant a section of a stem with leaf buds called a scion from a variety that has desirable traits into the cut.  In time the two pieces fuse together allowing for growth of the scion.  Eventually, blossoms on the scion will be pollinated and will produce a consistent variety of fruit with the desired traits.  For more information and pictures of the grafting process, please visit the website Apple Tree Propagation: Grafting.

The goal of apple breeding is to continuously produce quality apples with desirable traits.  Cross breeding and genetic engineering are two methods that have allowed breeders to produce better quality apples.

Interest Approach – Engagement

  1. Tell students that there are thousands of varieties of apples grown in the United States. Most of the varieties will not be familiar to them because they are only found in orchards grown for research, the development of new apple varieties, or hobby orchards. Challenge students to try to list the top 10 apple varieties in the United States. These varieties are more likely to be familiar to your students in addition to other local varieties.
  2. Ask students to think about what their favorite apple is. Ask them why that variety is their favorite apple and lead into a discussion about various apple traits such as sweetness, tartness, flavor, crunchiness, color, etc. 
  3. Ask students how these different apple varieties came to be.
  4. Ask your students, "How were multiple varieties of apples developed... each with a different color, texture, and taste?" Allow students to offer their ideas using their prior knowledge as you transition to Activity 1.

Procedures

Important
This lesson investigates phenomenon that can be observed in apples. Natural phenomena are observable events that occur in the universe that we can use our science knowledge to explain or predict.

Phenomenon-Based Episode: What makes apple varieties different?
Disciplinary Core Ideas: Heredity: Inheritance and Variation of Traits and Biological Evolution: Unity and Diversity

National Agricultural Literacy Outcome Theme: Science, Technology, Engineering, and Math

QuestionScience and Engineering PracticesStudent Engagement in PracticesExplanation
  1. What makes apple varieties different?

 

  • Planning and Carrying Out Investigations
Students carry out investigations to compare the Braeburn, Royal Gala, and Jazz apples. Students ask and refine questions that lead to descriptions and explanations about the different traits found in apples such as color, taste, texture, and size. The traits found in apple varieties are determined by their genetic makeup, or genotype. Heritable traits are passed from parent to offspring.
  1. How are new varieties of apples created?
  • Asking Questions and Defining Problems
Students use science to ask and refine questions that lead to explanations about the process of selectively breeding apples to produce new apple varieties with desirable traits. Apple breeders cross pollinate the flowers of specific apple varieties (sexual propagation) and then plant the seeds to obtain a tree and apples genetically different than the parent trees. It takes hundreds or even thousands of crosses, to find the desirable result. 
  1. What makes every apple of a given variety taste and look the same?
  • Constructing Explanations and Designing Solutions
Students can use science to explain that forms of asexual propagation produce genetically identical offspring. In contrast to apple breeders, apple farmers use grafting to produce new apple trees. This form of asexual plant propagation allows the genetics of each variety of apple to be exact clones, therefore producing a consistent crop of apples for consumers. 

 

     

Activity 1: Apple Genetics - Making them Different (Episode Questions 1 and 2)

  1. Give each student one copy of the Apple Genetics worksheet. Divide the class into small groups of students (2-4).
  2. Give each group of students the following supplies:
    • 1 paper plate (this will be the cutting board as well as an area to keep the apples)
    • 1 Braeburn Apple
    • 1 Royal Gala Apple (Note: DO NOT hand out the Jazz apple yet).
    • 1 knife (or pre-slice apples)
  3. Have students draw a line down the center of their paper plate and label each side with "Gala" or "Braeburn." The apples will look similar, so it will be important to avoid confusing the two apples.
  4. Have students complete "Part 1" and "Part 2" of the worksheet and then stop.
  5. Project the Apple Genetics PowerPoint for students to see. Using slide 2, hold a brief class discussion about the traits they have observed in the apples so far. Draw on the student's prior knowledge of heredity and genetics to conclude that each trait is an expression of its genotype.
  6. Use slide 3 of the PowerPoint to review vocabulary if needed. Make sure students are familiar with the terms.  
  7. Have students complete "Part 3" of the worksheet to review the possible genotypes of the Gala and Braeburn apples. These genotypes can be found on the worksheet and slide 4-5 of the PowerPoint.
  8. Once students have finished their Punnet squares, give each group of students a Jazz apple. Students will follow the same procedure and complete "Part 4" and "Part 5" of the worksheet. 
  9. Facilitate a class discussion about the 3 varieties of apple (slide 6). Reveal to the students that the Jazz apple is a cross between the Gala and Braeburn apple. Using slide 7, share a few more facts about the Jazz Apple.
  10. Talk about the concept of crossbreeding and how it is used to produce better quality organisms (slide 8).
  11. Draw back to the podcast about the Honeycrisp apple from the beginning of the lesson. Explain that the Honeycrisp apple (slide 9) was also developed by crossbreeding, and is a competitor of the Jazz apple.
  12. Summarize with students by connecting what they know about genetics with what they have learned about apples:
    • Genes determine genetic traits found in apples such as color, taste, and texture.
    • To develop a new, improved variety of apple, apple breeders cross pollinate apple varieties. This form of sexual reproduction results in an offspring (seed) that is genetically different from the parent trees.
    • Scientists use a knowledge of genetics and heredity to cross breed apples and produce new varieties of apples. The Jazz and Honeycrisp apples are examples.

Activity 2: Apple Genetics - Keeping Them the Same (Episode Question 3)

  1. Ask students if they have ever eaten Jelly Belly jelly beans. Have they ever eaten or heard of the Jelly Belly jelly beans that have "bad" flavors like toothpaste, stinkbug, or stinky socks? (Perhaps in the game Beanboozled.) While this may be a fun game or practical joke, have a discussion with your students about what they (as consumers) want in their food. Conclude that every time they purchase milk, meat, bread, vegetables... or an apple, they want it to taste consistently the same without surprises.
  2. Students have just learned how new varieties of apples are created. Ask, "How do apple farmers all across the nation grow specific varieties of apple that all taste and look the same? For example, how does a Granny Smith always taste like a Granny Smith and a Gala always taste like a Gala?" Does a [Granny Smith] grown in one region of the country taste the same as a [Granny Smith] grown in another region of the country?
  3. To discover the answer, show Apple - How Does it Grow? 
  4. From the video, students should recognize grafting as the answer to the question. Apple farmers do not grow trees from seed, they use a technique called grafting (slide 10).
  5. Ask students, "What is the genetic similarity of two trees grafted from the same source?" (They are genetically identical clones. Therefore, every apple tree grafted from the same source will produce apples with the same genetic makeup.)
  6. Summarize with students by connecting what they know about genetics with what they have just learned about apples:
    • Grafting, a form of asexual propagation is used by apple farmers to produce the apples we eat. It produces apples consistent to consumer expectations for each variety of apple by eliminating the genetic variability of sexual propagation methods.
Important

In addition to growing a consistent apple crop, farmers use grafting to propagate apple trees because it is significantly faster than growing a tree from seed. An apple tree grown from seed will take 6-10 years to produce fruit. A grafted apple tree will take 2-3 years depending on the type and size of the graft.

Concept Elaboration and Evaluation:

After completing these activities, have students create a Venn Diagram to list both the similarities and differences found in sexual and asexual propagation methods. Discuss the benefits and drawbacks of each. 

Important
Three Dimensional Learning Proficiency: Disciplinary Core Ideas
Organisms reproduce, either sexually or asexually, and transfer their genetic information to their offspring.

 

Phenomena Episode Extensions:

Effective phenomena-based instruction continues to evolve as students learn. New questions should arise throughout the learning process. The following questions may arise providing opportunity for other episodes in this storyline:

  • Why can other fruits and vegetables be propagated with sexual reproduction (seeds) and produce a consistent crop, but apples cannot?
  • What makes a Granny Smith apple so tart?
  • What makes an apple (such as the Honeycrisp) crunchy?
  • How was the Opal apple selectively bred to not brown after it is cut?
  • How was the Arctic® apple genetically engineered to be non-browning? 

Important
We welcome your feedback! Please take a minute to tell us how to make this lesson better or to give us a few gold stars!

 

Enriching Activities

  • If cut apples are in the room at the end of the lesson, ask students if they see any browning occurring. Discuss what causes this. Teach students about Arctic apples, a genetically modified apple which does not brown. Compare and contrast to the Opal apple, an apple variety selectively bred to be non-browning.

  • Show the 4-minute video clip, Have We Engineered The Perfect Apple? to see the science behind the taste of the Honeycrisp apple.

  • Listen to the NPR podcast "The Miracle Apple" or watch The Apple That Changed the World

Suggested Companion Resources

Agricultural Literacy Outcomes

Science, Technology, Engineering & Math

  • Describe how biological processes influence and are leveraged in agricultural production and processing (e.g., photosynthesis, fermentation, cell division, heredity/genetics, nitrogen fixation) (T4.6-8.b)
  • Provide examples of science and technology used in agricultural systems (e.g., GPS, artificial insemination, biotechnology, soil testing, ethanol production, etc.); explain how they meet our basic needs, and detail their social, economic, and environmental impacts (T4.6-8.i)

Education Content Standards

Within CAREER

Biotechnology Systems Career Pathway

  • BS.03.04
    BS.03.04
    Apply biotechnology principles, techniques and processes to enhance plant and animal care and production (e.g., selective breeding, pharmaceuticals, biodiversity, etc.).

Within SCIENCE

MS-LS4 Biological Evolution: Unity and Diversity

  • MS-LS4-4
    MS-LS4-4
    Construct an explanation based on evidence that describes how genetic variations of traits in a population increase some individuals’ probability of surviving and reproducing in a specific environment.
  • MS-LS4-5
    MS-LS4-5
    Gather and synthesize information about technologies that have changed the way humans influence the inheritance of desired traits in organisms.

MS-PS1: Matter and Its Interactions

  • MS-PS1-2
    MS-PS1-2
    Analyze and interpret data on the properties of substances before and after the substances interact to determine if a chemical reaction has occurred.

Common Core Connections

Reading: Anchor Standards

  • CCSS.ELA-LITERACY.CCRA.R.7
    CCSS.ELA-LITERACY.CCRA.R.7
    Integrate and evaluate content presented in diverse media and formats, including visually and quantitatively, as well as in words.

Mathematics: Practice Standards

  • CCSS.MATH.PRACTICE.MP2
    CCSS.MATH.PRACTICE.MP2
    Reason abstractly and quantitatively. Students make sense of quantities and their relationships in problem situations. They bring two complementary abilities to bear on problems involving quantitative relationships: the ability to decontextualize—to abstract a given situation and represent it symbolically and manipulate the representing symbols as if they have a life of their own, without necessarily attending to their referents—and the ability to contextualize, to pause as needed during the manipulation process in order to probe into the referents for the symbols involved. Quantitative reasoning entails habits of creating a coherent representation of the problem at hand; considering the units involved; attending to the meaning of quantities, not just how to compute them; and knowing and flexibly using different properties of operations and objects.
  • CCSS.MATH.PRACTICE.MP4
    CCSS.MATH.PRACTICE.MP4
    Model with mathematics. Students can apply the mathematics they know to solve problems arising in everyday life, society, and the workplace. Students who can apply what they know are comfortable making assumptions and approximations to simplify a complicated situation, realizing that these may need revision later. They are able to identify important quantities in a practical situation and map their relationships using such tools as diagrams, two-way tables, graphs, flowcharts and formulas. They can analyze those relationships mathematically to draw conclusions.

 

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