Question

oxygen levels are lowest in what section in the diagram

Answer 1

Introduction

This course explores how information contained in DNA is used, explaining the flow of information from DNA to RNA to protein. Also introduced are the concepts of transcription (as occurs between DNA and RNA) and translation.

This OpenLearn course provides a sample of Level 1 study in Science.

Learning outcomes

After studying this course, you should be able to:

understand how the linear sequence of DNA within a gene is related to the linear sequence of amino acids of a proteinunderstand how the information in DNA is carried via RNA to make a proteinunderstand how RNA is synthesised from DNA by the process of transcriptionunderstand where the processes of transcription and translation occur within the cell.1 Using information stored in DNA

One important property of DNA is that it carries genetic information in the simple coding language of just four bases. These bases, which can be arranged in a huge variety of sequences, represent a vast potential store of information. In this course, we consider how this information is used by the cell. The key structural feature of complementary base pairs, which plays an important role in both stability and replication, is also the basis for how DNA functions as genetic material.

How does the simple coding language of DNA relate to the nature of the gene; that is, how do genes function? Genes, composed of DNA, specify proteins. How genes do this is the topic of this course. The essence is that the structure of DNA can be related directly to the structure of proteins, which come in a huge range of sizes and shapes, and this diversity arises from different combinations of just 20 amino acids. In the text that follows we will examine how the simple coding language of just four letters (bases) in DNA contains information for thousands of different proteins, each with its own unique sequence of amino acids.

The production of proteins is a far more complex process than the more straightforward process of DNA replication, partly because many other molecules are involved. Below we will review the overall process and then go on to examine each step in turn.

2 One gene–one protein

A gene is a short section of a long DNA double helix molecule, which comprises a linear sequence of base pairs.

SAQ 1

What is the basic (primary) structure of a protein?

Answer

A protein is a linear sequence of amino acids.

There is a direct and specific relationship between the linear sequence of base pairs that makes up a gene, and the linear sequence of amino acids in a protein molecule. This relationship, presented in a very simplistic manner in Figure 1, is known as the one gene-one protein hypothesis. Each gene codes for a different protein. Thus the gene for haemoglobin specifies the protein haemoglobin, and the gene for myoglobin specifies the protein myoglobin. How the DNA sequence of a gene gives rise to the protein, i.e. how the protein is synthesized, is the subject of the rest of this course.

Figure 1 The relationship between a gene and the protein for which it codes. DNA is shown here as a double strand with the helix unwound.