DNA, Genes, and Proteins
From DNA to Protein
Specific proteins perform a variety of important functions in the body. They may act as catalysts to control
reactions, act as antibodies in the immune system, transport materials around the body, form the physical
structures that allow organisms to move, or control the movement of substances into and out of cells. The
instructions for making specific proteins are controlled by genes housed in DNA. Since genes control the
production of proteins, they have enormous influence on the physical characteristics of an organism.
Francis Crick, one of the discoverers of the structure of DNA, is also known for formulating the central dogma
of molecular biology. This dogma states that information flows from DNA to RNA to protein, but not from the
protein back to RNA or DNA. The pathway of protein information runs one way:
DNA → RNA → protein
Protein production occurs in two phases:
During transcription, information in DNA is transcribed, or rewritten, onto a strand of
messenger RNA (mRNA).
During translation, the information written onto the mRNA is used to assemble a protein.
Transcription, the process by which information from DNA is transferred to mRNA, occurs in the nucleus of
the cell. DNA is unwound at a specific gene, and mRNA is formed via complementary base pairing at one
strand of the DNA.
Transcription can be described in three steps:
binds to the
region of DNA at the start of a gene.
RNA polymerase unwinds the DNA and starts to assemble the mRNA.
The RNA polymerase moves down the DNA strand, assembling the mRNA from 5' to 3'.
Through complementary base pairings, the mRNA assembles along one strand of DNA, known as the
The RNA polymerase reaches a stop signal, a certain series of bases within the DNA.
Transcription ceases, and the mRNA dissociates from the template strand of DNA.
As a result of complementary base pairings, the template strand 3' TACTTGGCGATT 5' would be transcribed
into the following mRNA: 5'AUGAACCGCUAA 3'.