Nucleic Acids

DNA and RNA are the nucleic acids in cells.

 Nucleic acids are polymers made up of monomers called nucleotides.

 Nucleotides have three parts.

1. phosphate group

2. 5-carbon sugar

3. nitrogen-containing base

DNA compared with RNA


The 5-carbon sugar differs between DNA and RNA.

There are four possible nitrogen-containing bases in DNA or RNA.

The bases in DNA are A,T,G,C

The bases in RNA are A,U,G,C

The phosphate groups and sugars of nucleotides are linked to form the backbone of a DNA or RNA molecule.

RNA structure


The nitrogen-containing bases show specific complementary base pairing.

In DNA or RNA, G is always paired with C.

In DNA, T is always paired with A.

In RNA, U is always paired with A.

DNA is a double helix formed from two spiral strands. RNA is only single stranded


DNA structure



DNA holds the recipes for making proteins

Complementary base pairing allows DNA to pass genetic information to RNA.

The information in DNA is present in a triplet code where every three bases stands for one of the 20 amino acids.

The determination of the sequence of human DNA was a large project called the Human Genome Project.

To learn more about the Human Genome Project, click here. When you click on the link, a new window will open to another website which describes the Human Genome project in detail.


Relationship Between Proteins and Nucleic Acids

The order of amino acids in a protein determines its shape and function.

The DNA contains the instructions for the sequence of amino acids for each protein.

Errors or faults in the DNA can change the function of the encoded protein and lead to diseases like sickle cell disease. Click here to open a new window that describes sickle cell disease.


 Toggle open/close quiz question

The purpose of the nucleic acids is to:
    a.serve as an energy source that a cell can burn
    b.break down cellulose
    c.keep the water in cells from freezing the information needed to make a specific protien


Extra Help


More about nucleic acids 

Review of chemistry and macromolecules