Bio-Lec57-Lec58-DNA Technology.pptx - Amazon S3

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14 Δεκ 2012 (πριν από 4 χρόνια και 11 μήνες)

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NIS
-

BIOLOGY


Lecture 57


Lecture 58

DNA Technology



Ozgur

Unal

1

Genetic Engineering

2


What comes to your mind when you hear the term “Genetic
Engineering”?

Genetic Engineering

3


Genetic engineering
is the technology that involves
manipulating the DNA of one organism in order to insert
exogenous DNA
(DNA of another organism).


Example:
Researchers have inserted a gene for a
bioluminescent protein called green fluorescent protein (
GFP
)
into various organisms.


GFP is naturally present in jellyfishes in the north Pacific Ocean


Some organisms have been genetically

engineered to synthesize GFP.


Figure 13.3


mosquito larvae


Genetic Engineering

4


Selective breeding is used to produce plants and animals with
desired traits.


Similarly, genetic engineering can be used to increase or
decrease the expression of specific genes in selected organisms.


Genetic engineering has many applications


human health,
agriculture etc.


But
how are these

engineering processes

achieved?

DNA Tools

5


An organism’s
genome
is the total DNA present in the nucleus
of each cell.


Human genome
contains around
25,000 thousand genes.


In order to study a specific gene, DNA tools can be used to
manipulate DNA and to isolate genes from the rest of the
genome.

DNA Tools

6

Restriction Enzymes:


Some types
of bacteria contain powerful defenses against
viruses.


These cells contain proteins called
restriction enzymes
that
recognize and bind to specific DNA sequences and cleave the
DNA within that sequence.


A restriction enzyme, also called

endonuclease
, cuts the viral DNA into

fragments after it enters the bacteria.


There are many different types of

restriction enzymes.

DNA Tools

7

Restriction Enzymes:
EcoRI


One restriction enzyme that is widely used by scientists is
EcoRI
.


EcoRI specifically cuts DNA containing

the sequence GAATTC.


EcoRI cuts this sequence such that it

produces complementary
sticky ends
.


Not all restriction enzymes create

sticky ends!


http://highered.mcgraw
-
hill.com/olc/dl/120078/bio37.swf


DNA Tools

8

Gel Electrophoresis:


An electric current is used to separate the DNA fragments
according to the size of the fragments in a process called
gel
electrophoresis
.


Check out
Figure 13.5
!!


When an electric current is applied, the DNA fragments move
toward the positive end of the gel.


The smaller fragments move faster

than the larger ones.


Portions of the gel containing each

band can be removed for further

study.

Recombinant DNA Technology

9


After DNA fragments have been separated by gel
electrophoresis, fragments can be removed and combined with
DNA fragments from another source


recombinant DNA


Large quantities of recombinant DNA are needed to study them


In order to transfer the recombinant DNA into a bacterial cell,
scientists use a carrier (also called
vector
)


Plasmid
or
Virus


Plasmids are small, circular and double stranded DNA
molecules that occure naturally in bacteria and yeast.

Recombinant DNA Technology

10


If a plasmid and a DNA

fragment obtained from

another genome have been

cleaved by the same

restriction enzyme, the ends

of each DNA fragment will be

complementary and can be

combined.


An enzyme normally used by

cells in DNA repair and

replication, called
DNA ligase
,

joins the two DNA fragments

chemically.


Check out
Figure 13.6
!!

Gene Cloning

11


Gene cloning is used to make large quantities of recombinant
plasmid DNA.


Some bacterial cells take up the recombinant plasmid DNA into
them through a process called
transformation
.


Bacteria can be transformed using electric pulsation or heat.


Large quantities of identical bacteria, each containing the
inserted DNA molecules, can be produced through a process
called
cloning
.


Check out
Figure 13.7
!!

DNA Sequencing

12


The sequence of the DNA

nucleotides of most

organisms is unknown.


Knowing the sequence is

a valuable is information

to have.


Check out
Figure 13.8
for

the steps in DNA

sequencing technique!!

Polymerase Chain Reaction

13


Once the sequence of a DNA fragment is known, a technique
called the
polymerase chain reaction
,
PCR
, can be used to make
millions of copies of a specific region of a DNA fragment.


PCR is extremely sensitive and can detect a single DNA
molecule in a sample.


Follow the steps of PCR from the book and check out
Figure
13.9
!!

http://www.dnalc.org/resources/animations/pcr.html

http://www.maxanim.com/genetics/PCR/PCR.htm


Check out
Table 13.1
for the differences in the DNA
manipulation techniques
we learned so far.