DNA Components and Structure Name: __________________
Introduction
Nucleic acids are molecules that are essential to, and characteristic of, life on Earth. There are two basic types of nucleic
acid, DNA (deoxyribonucleic acid) and RNA (ribonucleic acid). This exercise will focus on DNA, although ways in which it
differs from RNA will also be presented.
DNA is found in all organisms from the smallest bacteria to humans. DNA has the same composition and structure in all
organisms! DNA has two important functions.
1. It is the genetic material that is passed from one generation to the next.
2. It is the coded information that tells cells how to make proteins.
Part I - Components of Nucleic Acids
Nucleic acids have the same basic structure in all organisms. Nucleic acids are polymers (long chains) of similar subunits
(pieces) called nucleotides. A nucleotide is composed of three different molecules, a phosphate group, a sugar, and a
nitrogen base. These three components are described below.
1. A Phosphate group is negatively charged and gives DNA molecules a negative charge. Will water be attracted
or repelled by the phosphate group? Why?
2. A nitrogen base – Four different nitrogen bases are found in DNA. They are adenine (A), cytosine (C), guanine
(G) and thymine (T). In RNA, thymine is replaced by uracil (U). Structures of the nucleotides are shown below.
There are two different types of nitrogen base; the pyrimidines that have one ring and the purines that have two
rings. Examine the nitrogen bases below. Below each base note the following by circling the correct answer
1 – whether it is found in DNA, RNA, or both
2 – whether it is a pyrimidine or a purine
