In 1973, Stanley Cohen and Herbert Boyer conducted an experiment
that revolutionized genetic studies in biology. They isolated the gene
that codes for ribosomal RNA from the DNA of an African clawed
frog and then inserted it into DNA of E coli bacteria.
The process of manipulating genes for practical purposes is called
Genetic engineering may involve building
from two or more different organisms.
Steps in a Genetic Engineering Experiment
The DNA from the organism containing the gene of
interest is cut by restriction enzymes.
bacterial enzymes that recognize and bind to specific short
sequences of DNA, and then cut the DNA between specific
nucleotides within the sequences. The DNA from a vector also is
is an agent that is used to carry the gene of interest
into another cell. Commonly used vectors include viruses, yeast and
, are circular DNA molecules that can replicate
independently of the main chromosomes of bacteria.
Making recombinant DNA
The DNA fragments from the organism
containing the gene of interest are combined with the DNA
fragments from the vector. An enzyme called
to help bond ends of DNA fragments together.
In this process, many copies of the gene of interest are
made each time the host cell reproduces. Remember that bacteria
, producing identical offspring. When a
bacterial cell replicates its DNA, its plasmid DNA also replicates.
Cells that have received the particular gene of interest
are distinguished, or separated, from the cells that did not take up
the vector with the gene of interest. The genes can
the gene of interest to make the protein coded for in the
THE HUMAN GENOME PROJECT
The sequence of an organism’s genome is the identification of all base
pairs that compose the DNA of the organism. The project is a
research project that has linked over 20 scientific laboratories in 6
countries cooperating to identify all
base pairs of the
DNA that makes up the human genome.
The Number of Human Genes
Human cells contain only 30,000 to
40,000 genes. When scientists had counted unique human mRNA
molecules, they had found over 120,000.
Genetically Engineered Drugs and Vaccines
Genetically Engineered Medicines
Used for treatment of
Human growth hormone
is a solution containing all or part of a harmless version of a
causing microorganism). When a vaccine is
injected, the immune system recognizes the pathogen’s surface
proteins and responds by making defensive proteins