Students should be first instructed on the basics of genetics. Genetics is the field of biology that studies genetic material called deoxyribonucleic acid or DNA. DNA is double stranded molecule containing four nitrogenous bases called adenine, guanine, cytosine and thymine labeled as A, G, C and T. Without a grasp of the fundamental properties of DNA, it is difficult for students to understand the purpose of DNA. A group of three bases is called a triplet and provides the coding information to determine a single amino acid. A chain of amino acids chemically bound together forms a polypeptide chain called a protein. A group of coded bases that determines an entire protein is called a gene.
One important topic in genetics is the basic understanding of genotypes and phenotypes. A phenotype is an observable trait such as eye or hair color. Students can learn that color results from production of colorful proteins called pigments. The genetic material, DNA provides the code for producing a protein. Teachers can use observable phenotypes as laboratory exercise allowing students to look at simple characteristics such as an ability to curl the tongue or whether a student has attached or unattached earlobes. The observable characteristics can be used to explain how genes function to determine phenotypic characteristics.
The work performed by Gregory Mendel led to an important understanding that complex organisms, plants and animals, possessed two copies of each gene. The genes are not necessarily identical. One copy of a gene may determine a pink flower while another determines the flower is blue. The research conducted by Mendel also led to the discovery that one gene copy is dominant and the other is recessive. Only one dominant gene in a gene pair needs to be present for the dominant trait to be observed. A simply classroom activity can introduce students to dominant and recessive genes. Counting students with a particular trait, attached or unattached earlobes, can produce statistics that can determine which trait is dominant.
Cells divide and the DNA must be divided equally between the two newly created daughter cells. Cell division can posse a particular problem unless DNA duplicates first to produce identical copies. DNA replication is a semi-conservative process. DNA is a double stranded molecule with one strand opposite the other. During replication, the strands separate and the nitrogenous bases bind to form two new daughter strands. The process is considered semi-conservative because each new strand consists of one parental strand and a newly formed daughter strand. Duplicating the genetic material allows each new daughter cell to obtain an identical copy as the parent cell. The process of DNA replication can be demonstrated to students using simple models or pictures that provide visual aid. Exact copies are produced because A bases always match with T and G always matches with C in the double stranded molecule.
Once students master basics of genetics, students can begin to learn how genes function to determine proteins during the processes called transcription and translation. DNA provides a code consisting of three nitrogenous bases for each amino acid. The code is used to produce an intermediate messenger, called messenger ribonucleic acid or mRNA. Messenger RNA is a molecule similar to DNA and contains similar nitrogenous bases. The RNA copies the DNA by matching similar bases as in DNA replication. A second intermediate called transfer RNA recognizes the triplet code provided by mRNA and delivers an amino acid to a growing polypeptide chain. Each group of three bases on the mRNA equates to a specific amino acid until a complete protein is formed. This is a complex process demonstrated to a seventh-grade class. However, the basics to the process can be demonstrated with visual aids. Animated photos often work well.