Download 2013 Gen Tech Part 2

III Manipulating DNA
The Tools of Molecular Biology
The Tools of Molecular Biology
How do scientists make
changes to DNA?
The Tools of Molecular Biology
Scientists use different techniques to:
• extract DNA from cells
• cut DNA into smaller pieces
• identify the sequence of bases in a
DNA molecule
• make unlimited copies of DNA
The Tools of Molecular Biology
In genetic engineering,
biologists make changes in the
DNA code of a living organism.
The Tools of Molecular Biology
DNA Extraction
DNA can be extracted from most
cells by a simple chemical
procedure.
The cells are opened and the DNA is
separated from the other cell parts.
The Tools of Molecular Biology
Cutting DNA
Most DNA molecules are too large to
be analyzed, so biologists cut them
into smaller fragments using
restriction enzymes.
Which type of molecule is an
enzyme?
The Tools of Molecular Biology
Each restriction enzyme cuts DNA at a specific
sequence of nucleotides.
Recognition sequences
DNA sequence
Restriction enzyme EcoR I cuts
the DNA into fragments
Sticky end
The Tools of Molecular Biology
Separating DNA
In gel electrophoresis, DNA fragments are
placed at one end of a porous gel, and
an electric voltage is applied to the gel.
The Tools of Molecular Biology
Power
source
DNA plus restriction
enzyme
Longer
fragments
Mixture of
DNA
fragments
Gel
Gel Electrophoresis
Shorter
fragments
The Tools of Molecular Biology
DNA plus
restriction enzyme
First, restriction
enzymes cut
DNA into
fragments.
The DNA
fragments are Mixture of DNA
poured into wellsfragments
on a gel.
Gel Electrophoresis
Gel
The Tools of Molecular Biology
Power
source
An electric
voltage is applied
to the gel.
The smaller the
DNA fragment,
the faster and
farther it will
move across the
gel.
The Tools of Molecular Biology
Power
source
Longer
fragments
Shorter
fragments
Gel Electrophoresis
Using the DNA Sequence
Making Copies
Polymerase chain reaction (PCR) is a
technique that allows biologists to make
copies of genes.
Small amounts of DNA can be multiplied
making it easier to analyze.
Made possible by an enzyme found in a
bacterium living in hot springs in Yellow
Stone National Park.
Using the DNA Sequence
Polymerase Chain Reaction (PCR)
DNA heated to
separate strands
DNA polymerase adds
complementary strand
DNA fragment
to be copied
PCR cycles 1
DNA copies 1
2
2
3
4
4
8
5 etc.
16 etc.
Quiz
Restriction enzymes are used to
•
•
•
•
extract DNA.
cut DNA.
separate DNA.
replicate DNA.
During gel electrophoresis, the smaller the DNA
fragment is, the
•
•
•
•
more slowly it moves.
heavier it is.
more quickly it moves.
darker it stains.
The DNA polymerase enzyme found in bacteria
living in the hot springs of Yellowstone
National Park illustrates
• genetic engineering.
• the importance of biodiversity to biotechnology.
• the polymerase chain reaction.
• selective breeding.
A particular restriction enzyme is used to
•
•
•
•
cut up DNA in random locations.
cut DNA at a specific nucleotide sequence.
extract DNA from cells.
separate negatively charged DNA molecules.
During gel electrophoresis, DNA fragments
become separated because
•
•
•
•
multiple copies of DNA are made.
recombinant DNA is formed.
DNA molecules are negatively charged.
smaller DNA molecules move faster than larger
fragments.
END OF SECTION