Transcript 14.3 DNA techniques 2013 - OG

Techniques for Studying
Genetic Disorders
What techniques are used to
study human DNA?
How do you study DNA?
• How can scientists read DNA if the
smallest chromosome is 50 million
base pairs long?
• They cut, separate, and then
replicate DNA base by base
Step 1: Cutting DNA
• The enzymes produced by bacteria are
called restriction enzymes
– Like “molecular scissors”
• Restriction enzymes cut DNA into specific
pieces, called restriction fragments
• Each enzyme cuts DNA at a different
sequence, so scientists know the exact
bases in each piece
EcoRI – a restriction enzyme
• E. coli produces the restriction enzyme called
“EcoRI”
• Cuts DNA at the sequence G A A T T C
C TTAA G
• Leaves single-stranded overhangs, called
“sticky ends,” with the sequence AATT
• The sticky ends can
bond, or “stick,” to a
DNA fragment with the
complementary base
sequence
Step 2: Separating DNA
• Once DNA has been cut by restriction
enzymes, it must be separated by
fragment size
• Gel electrophoresis – technique that
separates DNA fragments by SIZE using
an electric current through a porous gel
Gel electrophoresis
• A mixture of DNA
fragments is placed at one
end of a porous gel
• When an electric voltage
is applied to the gel, DNA
molecules—which are
negatively charged —
move toward the positive
end of the gel
• The smaller the DNA
fragment, the faster and
farther it moves
DNA and Forensics
• Which suspect
committed the crime?
DNA and Paternity Testing
The Human Genome Project
• In 1990, the United States, along with several
other countries, launched the Human Genome
Project.
• The main goals: to sequence all 3 billion base
pairs of human DNA and identify all human
genes.
• Other important goals included: sequencing the
genomes of model organisms to interpret human
DNA, developing technology to support the
research, exploring gene functions, studying
human variation, and training future scientists.
New fields of study from HGP
• The Human Genome Project opened the doors
for a new field of study called bioinformatics
• Bioinformatics combines molecular biology
with information science. It is critical to
studying and understanding the human
genome
New fields of study
• Bioinformatics also launched a more
specialized field of study known as
genomics—the study of whole genomes,
including genes and their functions
What we’ve learned from The
Human Genome Project
• Identified genes and particular sequences in
those genes with numerous diseases and
disorders
• Identified about 3 million locations where singlebase DNA differences occur in humans, which
may help us find DNA sequences associated with
diabetes, cancer, and other health problems.
• This information is free and public on the
internet
New questions to consider
• Who owns and controls genetic information?
• Is genetic privacy different from medical
privacy?
• Who should have access to personal genetic
information, and how will it be used?
• In May 2008, President George W. Bush
signed into law the Genetic Information
Nondiscrimination Act, which prohibits U.S.
insurance companies and employers from
discriminating on the basis of information
derived from genetic tests
What to Know for Test:
• How scientists cut DNA: Restriction fragments,
restriction enzymes, EcoRI
• Gel electrophoresis: what is it? How does it
work? How does DNA get separated on the
gel?
• Goals of the Human Genome Project
• New problems arisen from the HGP
• New fields of study: bioinformatics, genomics,
• What’s been done about genetic privacy and
why?
– George Bush’s legislation