4-H Science Blast in the Class: What Genes DoDOWNLOAD
June 5, 2020 - Author: Michigan State University Extension
- To understand that, as a result of genetics, offspring are very much but not exactly — like their parents.
- To define and describe “genes.”
- To compare and contrast inherited traits using different combinations of genes.
Grade Level: 1–7
Education Subject: Science
Success Indicators: After participating in this activity learners will be able to:
- Explain why offspring share some traits with their parents and not others.
- Define and explain the difference between “dominant traits” and “recessive traits.”
Materials and Methods
Preparation Time: 30 minutes
Lesson Time: 30 minutes
- Pencils or pens
- Writing paper
- Five colors of pipe cleaners in two lengths (at least one per learner of each color and length)
- Ten paper bags
- Construction paper
- Markers or crayons
- Flip chart (or chalkboard or whiteboard)
You’ve probably noticed that offspring often resemble one or both of their parents. This is true for every living thing, whether plant or animal. In the 1860s, Gregor Mendel, an Austrian monk, decided to study pea plants to find out why parents pass along some but not all of their traits to their offspring. He looked at single characteristics — for example, plant height — instead of trying to figure out the whole genetic picture at one time. By working carefully, Mendel discovered the following fascinating facts:
The information for deciding traits is carried in something Mendel called “units” (which we now call “genes”). Genes tell organisms how to build and manage cells. Mendel figured out that parent pea plants each have two units that code for seed shapes, height, color and other characteristics, and that each parent plant passes one unit for each trait to the plants in the next generation. (Mendel didn’t actually see these genes because they’re microscopic, and microscopes hadn’t been invented yet.)
This genetic information keeps its identity from generation to generation. Mendel figured out that parents pass units (genes) to their offspring, which pass the units down to their offspring and so on. The information for some traits is dominant over that of others. Mendel found that some offspring had unexpected phenotypes, or physical traits. He explained this by using the terms “dominant” and “recessive.” A dominant unit (gene) is always expressed in offspring. A recessive unit (gene) may or may not be.
- Read the activity and gather the supplies from the materials list.
- Recreate the chart that follows on a flip chart or the chalkboard or whiteboard.
- Label and fill 10 bags, five representing Mom’s genes and five representing Dad’s genes. In each case, the number of pipe cleaners in each bag should equal or exceed the number of learners or teams.
- Line up the 10 bags on a table or desk at the front of the room.
- Tell the learners that they’re going to make a human using pipe cleaners. The pipe cleaners will represent the genes that control the various traits their humans will inherit. Tell them that the traits were chosen as examples because they’re coded for by single genes, and that many other traits are coded for by more than one gene. These traits are also affected only by the genes and that there are many traits that are affected by both genes and environmental conditions and nutrition as well.
- Have the learners (or a representative from each team, if they’re working in teams) take turns picking one pipe cleaner from each bag.
- Next have them lay out their pipe cleaners, and using the chart you prepared earlier, determine what traits their humans have. (Note: You also could have the students draw their humans, indicating what specific traits are represented.)
- Have the learners or teams share their humans’ phenotype (physical traits) and genotype (genetic) information. Record this information on a flip chart or board.
Check for Understanding:
Ask the group the following questions.
- Why do offspring generally look like their parents? (Because both parents contribute genes to their offspring.)
- Could two brown-eyed parents have a blue-eyed offspring? (Yes. The gene for blue eyes is recessive, but if both parents carry it, their offspring may inherit it.)
- How could Mendel produce a short plant from tall ones? (By crossing two plants that both carried the recessive gene for plant height [t].)
- What would happen when two short plants are bred? (All of their offspring would be short because it would be genetically impossible for those two plants to produce tall plants. The genes for short plants are recessive, so two parents with the recessive phenotype cannot produce tall offspring — the dominant phenotype.)
- How could you apply the information from this lesson in real life? (Livestock producers use genetic information all the time to help them decide which females to breed with which males and which animals to keep and which to cull (remove from the herd or flock). Animals with undesirable recessive traits would be culled.)
- How might environmental factors influence a person’s phenotype? (Nutrition, exercise and other factors influence wellness and appearance.)
- What environmental factors might change how a human looks or develops? (Poor nutrition can affect height, weight, color, strength of bones and teeth, and other traits. Vigorous exercise and play can help develop muscles.)
- Are the physical characteristics demonstrated in this activity an example of inherited or environmental influence on phenotype? (These traits are all example of traits that are 100 percent controlled by genes. So they are all inherited.)
- What is a gene? (A hereditary unit that carries and stores the information that helps control various physical, mental and behavioral characteristics in living things.)
- What are recessive genes? (Genes that are not expressed when combined with dominant ones.)
- Give some examples of recessive traits in humans. (Blue eyes, inability to roll the tongue, unattached earlobes, more than five fingers on each hand.)