Article
Genetics is an important part of biology because it explains how characteristics are inherited from one generation to another. Students preparing for the TEAS Science section should understand the basic structure of DNA, how genes work, and how genetic information is passed from parents to offspring. These concepts become easier when you understand how the different components fit together.
1. What is DNA?
DNA stands for deoxyribonucleic acid. It is the molecule that stores genetic instructions used in the growth, development, functioning, and reproduction of living organisms. DNA has a structure commonly described as a double helix, which resembles a twisted ladder. The sides of the ladder are made from sugar and phosphate molecules. The steps are formed by pairs of nitrogenous bases. There are four main DNA bases: - Adenine (A) - Thymine (T) - Cytosine (C) - Guanine (G) The bases pair in a specific way: adenine pairs with thymine, while cytosine pairs with guanine. This pairing matters because it lets DNA copy accurately during cell division.
2. Understand genes and chromosomes
DNA is organized into structures called chromosomes. A gene is a specific section of DNA that contains instructions for producing a functional product, often a protein. In humans, most body cells contain 46 chromosomes arranged into 23 pairs. One chromosome in each pair is generally inherited from each biological parent. Genes influence many characteristics, including aspects of eye color, blood type, and other inherited traits. However, many characteristics are influenced by several genes and environmental factors.
3. What are alleles?
Alleles are different versions of the same gene. For example, a gene may have different alleles that contribute to variations in a particular characteristic. In basic genetics, alleles are often described as dominant or recessive. - A dominant allele can influence a trait when one copy is present in a simple dominant-recessive inheritance pattern. - A recessive allele generally influences the trait when two copies are present in that same simplified pattern. Not every genetic trait follows this pattern. Some traits involve multiple genes, incomplete dominance, codominance, or other inheritance patterns.
4. Learn how Punnett squares work
A Punnett square is a diagram used to predict possible combinations of alleles from two parents. Consider a simplified example in which: - B represents a dominant allele. - b represents a recessive allele. - Both parents have the genotype Bb. Each parent can pass either B or b to an offspring. The possible combinations are: B b B BB Bb b Bb bb The possible genotypes are: - BB: 25% - Bb: 50% - bb: 25% This means there is a 25% probability of the offspring having genotype bb in this example. These percentages describe probabilities across many possible outcomes, not guaranteed results for a particular family.
5. Understand mutations
A mutation is a change in the DNA sequence. Mutations can occur naturally when DNA is copied or because of exposure to certain environmental factors. Some mutations have little or no noticeable effect. Others can affect how proteins function and may contribute to inherited disorders or other health conditions. Mutations are also important in evolution because genetic variation provides material for natural selection.
6. How to study genetics for the TEAS
Start by learning the difference between DNA, genes, chromosomes, and alleles. These terms are related but do not mean the same thing. Next, practice identifying the base-pairing rules and solving simple Punnett square problems. Draw diagrams instead of relying only on written definitions. Finally, explain each concept in your own words. If you can describe how DNA contains genes and how genes are organized into chromosomes, you have developed a useful foundation.
Final tip
Do not study genetics as a collection of unrelated definitions. Focus on how DNA, genes, chromosomes, and inheritance connect.
