By: Meghan Thoreau, OSU Extension Educator, Community Development & STEM, Pickaway County
Candy DNA Model
Our STEM Club recently embarked on a sweet adventure into the fascinating world of DNA structure and genetics! In the “Make A Candy DNA Model” activity, 4th and 5th-graders got hands-on with science, using colorful candies to represent the four nitrogen bases – Adenine, Thymine, Cytosine, and Guanine paired together in a twisting latter we call a double helix. Nitrogenous bases, also known as nucleobases, are the building blocks of DNA. They are a type of organic molecule that contains nitrogen and plays a crucial role in storing and transmitting genetic information.
The information in the nitrogen bases are then transcribed into RNA (Ribonucleic Acid), which is another type of molecule that readies our genetic code to be packaged into a set of instructions called proteins. Proteins are the workhorses of the cell, and their functions are essential for maintaining life. The genetic code in DNA and RNA provides the blueprint for making these important proteins, which in turn determine the traits, characteristics, and functions of an organism in working order or in our case keep our human body healthy and happy.
- Immune system: Proteins like antibodies, cytokines, and complement proteins help recognize and respond to pathogens.
- Muscular system: Proteins like actin, myosin, and troponin work together to enable muscle contraction and relaxation.
- Structural proteins (bone system): Proteins like collagen, osteocalcin, and osteonectin provide structure and strength to bones, skin, and connective tissue.
- Neural signaling: Proteins like neurotransmitters, receptors, and ion channels help transmit and regulate signals in the nervous system.
- Blood: Proteins like hemoglobin, clotting factors, and lipoproteins play critical roles in oxygen transport, blood clotting, and lipid metabolism.
- Enzymes: Proteins that catalyze chemical reactions, such as digestive enzymes, metabolic enzymes, and DNA repair enzymes.
- Cell membrane: Proteins like receptors, transport proteins, and structural proteins help regulate what enters and leaves the cell, and maintain cell shape and function.
Afterwards they will engage in Trait Inventory and Genetics Practice Problems and Investigating Alien Genetics activities.
Trait Inventory/Genetics Practice Problems:
Students answered a traits survey, that helped them identify their physical characteristics (eye color, hair color, height, etc.) and other traits (tongue rolling, earlobe attachment, etc.). This activity helped students identify and record various physical characteristics about themselves and their classmates. The physical characteristics of an organism are known as its phenotype. This refers to the observable traits and features, such as: eye color, hair color, height, skin color, and other physical characteristics. Then expanded into the complexity of genetics by understanding dominant and recessive traits we call alleles. Alleles are different forms of the same gene, and they determine the phenotype, physical characteristics of an organism.
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Dominant Allele: Represented by an uppercase letter (e.g., “B” for brown eyes)
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Recessive Allele: Represented by a lowercase letter (e.g., “b” for blue eyes)
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Genotype: BB, Bb, or bb (think of the genetic makeup, the letter codes of each each parent possesses, but may not physically show)
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Phenotype: “Brown eyes” (BB or Bb) or “blue eyes” (bb) (think of the physical characteristics that results from the genotype
Understanding the relationship between genotype and phenotype is crucial in genetics, as it helps predict how traits will be inherited and expressed. Eye color is an easy way to start understanding how dominant/recessive traits work. There are three combinations of eye color punnet squares below:
- A dominant trait is expressed if an individual has one or two copies of the dominant allele (version of the gene).
- Dominant traits are often represented by an uppercase letter (e.g., “B” for brown eyes).
- Examples: brown eyes, dark hair, curly hair
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A recessive trait is only expressed if an individual has two copies of the recessive allele (one from each parent).
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Recessive traits are often represented by a lowercase letter (e.g., “b” for blue eyes).
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Examples: blue eyes, blonde hair, straight hair
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An individual can be homozygous dominant (BB), homozygous recessive (bb), or heterozygous (Bb) for a particular trait.
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Heterozygous individuals (Bb) will express the dominant trait, but can pass the recessive allele to their offspring.
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Understanding dominant and recessive traits helps predict the likelihood of certain traits being passed down from parents to offspring.
Students discuss the implications of their findings, exploring how traits are distributed within the group and how they might be influenced by genetics.
Investigating Alien Genetics Activity:
Students applied the genetic principles they learned to a fictional scenario, thinking creatively about how traits might be inherited by alien parents. Even through each student had the same parent Genotypes, they soon discovered the difference Phenotype their offspring can acquire through the random combinations of how dominate and recessive genes pair up. Students discuss their results, exploring the implications of genetic inheritance in this alien species and how it might differ from or resemble genetics on Earth.
