These are some common student misunderstandings about genetics based on education research. Keep them in mind while teaching – and address them as they come up.
Genes and DNA are separate things
Many students think of genes and DNA as separate things – specifically, that genes are what make you look like your family and DNA is for identification. The focus on DNA in crime solving in the media contributes to this view. A gene is actually a segment of a DNA molecule
Genes are only found in certain cells
Students may hold the view that genes are only found in certain cells, commonly in the blood, brain or reproductive system. It is important for them to understand that, except for mature red blood cells, all human cells contain DNA and therefore genes.
Different cells contain different genes
Students often think that different cells contain different DNA, for example, the DNA in their skin cells is different to the DNA in their heart cells. In fact, every cell in your body (other than gametes) contains the same DNA and consequently the same genes. However, not every gene is expressed in every cell. For example, the genes that code for muscle proteins such as actin and myosin are only expressed in muscle cells and not in the other cells in your body, even though the genes are present in those other cells.
We are all unique because we have different genes
Students may think we are all unique because we each have different genes. However, all humans have almost exactly the same genes, in the same order, along our chromosomes. Our uniqueness is a result of the different combinations of alleles that we inherit from our parents. This variance in alleles results in a unique combination of traits. (Note: Alleles are alternative forms of the same gene that occupy the same location on a chromosome).
Genes code directly for our traits
Students commonly think of genes as direct instructions for particular traits. In fact, genes code for proteins that make up our cells, tissues and organs, ultimately leading to our unique phenotype.
Single genes code for particular traits
The examples we use when teaching about genetics may lead to the view that particular traits are always coded for by a single gene. While there are a few traits that are determined by a single gene (for example, dimples and cleft chin), most traits are complex and are the result of the interactions between several genes.
We only have genes for the traits that are displayed
Students might think that we only have genes for the traits we display. In fact, at any given locus there are 2 alleles (alternative forms of the same gene). Different alleles of a gene generally serve the same function (for example, they code for a protein that affects eye colour) but may produce different phenotypes (for example, blue eyes or brown eyes) depending on which set of 2 alleles you have and whether 1 allele is dominant.
Inheritance involves an averaging of the genes from both parents
Some students view genetic inheritance as an averaging of the genes from both parents. For example, 1 short parent and 1 tall parent will result in a child of average height. However, our characteristics (such as height) are commonly controlled by a number of genes. A child’s genotype is a unique combination of genes from both parents and is not merely a blending of the two. In addition, dominance means that a child may display characteristics of only 1 parent.
Download the Word file (see link below) for references and further reading.