Course: Science Subtest II
Lesson: Genetics and Evolution
Topic: Inheritance of Traits      Page 11 of 18  

Genes, DNA and Chromosomes

The three words, genes, DNA, and chromosomes are often used interchangeably. So it is not surprising that many people confuse the three.

Genes are the basic units of inheritance. A gene is a segments of DNA that carries genetic information for a trait. Sometimes two genes are needed to determine a trait.

Deoxyribonucleic acid (DNA) is a double strand that carries thousands of genes on a single strand. Each gene has a specific location (called a locus) on the DNA. In most living organisms. DNA is made up of two DNA strands that are tightly wound around each other in a structure called a double helix.In most organisms, the DNA double helix is linear. However, bacterial chromosomes are circular rather than linear.

The double helix structure of DNA