Transcript Powerpoint

DNA Technology
Biotechnology
The use or alteration of cells or
biological molecules for specific
applications
Transgenics
Transgenic
“changed genes”
Recombinant DNA
DNA from different species mixed together
Natural or man-made
Whole organisms or cells
Possible because the genetic code is
universal
All life uses the same genetic code
(A,T,G,C)
Amplifying DNA
Need many copies for various DNA
tests from a small initial sample
Two techniques
Polymerase chain reaction (PCR)
Recombinant DNA technology
PCR
Done on molecules
Based on DNA replication
Rapidly replicates a selected sequence of
DNA in a test tube
Used to:
Establish blood relationships
Identify remains
Convict or exonerate suspects
Look at pathogens
Identify genes
Very sensitive but easily contaminated
Review of DNA Replication
A
T
A
T
C
G
C
G
G
C
G
A
T
A
T
A
T
Parental
molecule
of DNA
A
C
C
Nucleotides
Both parental
strands serve
as templates
T
A
T
A
T
G
C
G
C
G
C
G
C
G
C
T
A
T
A
T
A
T
A
T
A
Two identical
daughter molecules
of DNA
Requirements for PCR
Know parts of the DNA sequence to be
amplified
2 DNA Primers
Short, lab-made single-stranded DNA
One complementary for each strand in the DNA
segment to be amplified
Lots of nucleotides
Taq DNA polymerase
From Thermus aquaticus (lives in hotsprings)
A thermal cycler
PCR
Recombinant DNA (cloning)
Works in cells
Adds genes from one type of
organism to the genome of another
Requires:
Restriction enzyme
Vector
Donor DNA
Host bacteria
Restriction Enzymes
Figure 19.3a
Cloning Vectors
Carries DNA from the cells of one
species into cells of another
Any piece of DNA into which another
can be inserted
Types of Vectors
Which vector used depends on size of the
gene to be inserted
Plasmid
One type of cloning vector
Small circle of double-stranded DNA
Occurs naturally in some bacteria and yeasts
Creating Recombinant DNA
Molecules
Figure 19.3a
Figure 19.3b
Recombinant DNA
Figure 19.5
Selecting Recombinant DNA
Molecules
3 types of cells
Cells that lack plasmids
Cells that contain plasmids that do not contain a foreign
gene
Cells that contain plasmids that have the foreign gene –
WANT THESE
Plasmids can contain a gene for an enzyme that
catalyzes a reaction that makes a blue color
If a foreign gene inserts in the middle of this “blue” gene,
the bacteria containing the plasma will not produce the
blue color
Plasmids can contain a gene for antibiotic
resistance
When the antibiotic is applied to the bacterial cells, only
those with the plasmid will survive
Applications of Recombinant DNA
Drugs (e.g. insulin)
Pure, human versions
e.g. “humulin”
Transgenic plants
a.k.a. genetically modified (GM) plants
Transgenic animals
e.g. 3xTg-AD mouse
Transgenic Plants
Transgenic Animals
Isolating a Gene
Make a DNA probe
Strand of DNA complementary to the
one of interest
Attached to a radioactive or fluorescent
molecule
Complementary (cDNA) Library
Represents only protein-encoding
genes
Made from mRNAs
Represents the proteins being made in a
particular cell
Making a cDNA library
Extract mRNAs from cells
Use reverse transcriptase to make
DNA from RNA
Use DNA polymerase to make
double-stranded DNA