DNA Replication

Nucleic Acid Function
DNA Replication, Transcription & Translation​ 


When the DNA molecule is inactive, the bases are linked by these hydrogen bonds and the molecule is in its spiral-shaped state. When DNA is being used—either being copied (a process called replication) or being employed to build proteins (involving the processes of transcription and translation)—the DNA molecule must be opened up, essentially “unzipped” between the bases.

Article Summary: Nucleic acids, DNA and RNA, are the vital genetic blueprints for and builders of cellular proteins. Here is how DNA is copied and proteins are built.
Nucleic Acid Function: Replication & Gene Expression

​Page last updated: 8/2015

Instructor's Corner
Continued ... 
DNA Replication
Go to PAGE 2 >
Nucleic Acid Structure
Nucleic acids are large organic molecules made of building blocks called nucleotides. Each nucleotide has three main parts:
  • a pentose sugar called ribose
  • one or more phosphate groups
  • one of five cyclic nitrogenous bases

Nucleotide Chemical Structure
Phosphate-Sugar Backbone
Nucleotides are linked to each other by covalent bonds between phosphate of one nucleotide and sugar of next. Linked nucleotides are the phosphate-sugar backbone of nucleic acids, and their nitrogenous bases extend from this phosphate-sugar backbone like teeth of a comb.

The DNA Spiral Staircase
In deoxyribonucleic acid, DNA, hydrogen bonds form between specific bases of two nucleic acid chains, forming a twisted, double-stranded DNA molecule that looks like a spiral staircase, with the two sugar-phosphate chains as side rails and the base pairs forming the rungs.

Chemical Structure of DNA
DNA only contains the bases Adenine (A), Cytosine (C), Guanine (G) and Thymine (T), not Uracil (U). When bases pair up between the two DNA strands, a purine always pairs with a pyrimidine. Specifically Adenine and Thymine always pair up, and Cytosine (C) and Guanine (G) always pair up.

Virtual Cell Biology

The Virtual Cell Biology Classroom provides a wide range of free educational resources including Power Point Lectures, Study Guides, Review Questions and Practice Test Questions.
Endomembrane System of a Eukaryotic Cell, Mariana Ruiz
This article has 
3 pages: 
1  .  2 .  3
from the free STEM 
education site 
Science Prof Online
The bases found in nucleic acids include the double-ring purine bases Adenine and Guanine the single-ring, smaller pyrimidine bases of Cytosine, Uracil and Thymine.
DNA Semi-conservative Replication Illustration
Instructors Corner
 of Science Prof Online

You have access to a large collection of free science teaching materials used in high school and college-level introductory science courses. The SPO Instructors Corner has resources for teaching general science, anatomy & physiology, chemistry, cell biology genetics, immunology and microbiology.
Instructors Corner of Science Prof Online