Biology (Holt)

Section 1 Genetic Engineering

228 CHAPTER 11Gene Technology

Basic Steps of Genetic Engineering

Not too long ago, using bacteria to produce human insulin and

inserting genes into tomatoes and human cells were ideas that

existed only in science fiction books and movies. But now, the tech-

niques required to carry out these ideas have been developed and

are used daily.

In 1973, Stanley Cohen and Herbert Boyer conducted an experi-

ment 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 the DNA of Escherichia coli

bacteria, as summarized in Figure 1.During transcription, the bac-

teria produced frog rRNA, thereby becoming the first genetically

altered organisms. The process of manipulating genes for practical

purposes is called .Genetic engineering may

involve building —DNA made from two or more

different organisms.

The basic steps in genetic engineering can be explored by exam-

ining how the human gene for insulin is transferred into bacteria.

Insulin is a protein hormone that controls sugar metabolism.

Diabetics cannot produce enough insulin, so they must take doses of

insulin regularly. Before genetic engineering, insulin was extracted

from the pancreases of slaughtered cows and pigs and then purified.

Today, the human insulin gene is transferred to bacteria through

genetic engineering. Because the genetic code is universal, bacteria

can transcribe and translate a human insulin gene using the same

code a human cell uses in order to produce human insulin.

recombinant DNA

genetic engineering

Objectives

Describefour basic
steps commonly used
in genetic engineering
experiments.

Evaluatehow restriction
enzymes and the anti-
biotic tetracycline are
used in genetic
engineering.

Relatethe role of
electrophoresis and
probes in identifying a
specific gene.

Key Terms

genetic engineering

recombinant DNA

restriction enzyme

vector

plasmid

gene cloning

electrophoresis

probe

Cohen and Boyer produced the first genetically engineered organisms.

Figure 1 Genetic alteration of an organism

1.Cohen and Boyer used an African

clawed frog as their experimental

organism.

2.They isolated an rRNA

gene from one of its

chromosomes.

3.They inserted the gene into

bacteria. The bacteria produced

frog rRNA.

4B 6A 6B 6D

4B 6A 6B 6D

6A 11B 6D