Chap 13 Gene Technology

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23 Οκτ 2013 (πριν από 3 χρόνια και 11 μήνες)

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Chap 13 Gene Technology


Current events….what are we hearing
about “genetic technology”?


Controversial…. Why?


Produce new life forms


Long term effects unknown


Discrimination by employers or
insurance companies


???


Only about
.1%

of the human genome varies from
person to person (this can be used to ID individuals)

-

97% of the human genome is the
same
in all people

-

98% of our genetic make up
does not code for

proteins at all =
noncoding DNA

Noncoding DNA


Length

polymorphisms
= variation in the
length of the DNA molecule
between

known
genes (in the noncoding DNA).


Repeats in nucleotide sequences
(2
-
5 bases long)

are
common
-

can repeat a few times or many
times.


Variable number

tandem

repeats (
VNTR
)




The number of repeats at
specific loci

(location) on specific chromosomes varies
among individuals = can use for identification



You are unique!


The chance that another person has your pattern
of VNTRs has been CALCULATED


However these patterns are
inherited



Manipulating DNA

Scientists use their knowledge of the structure of
DNA and its chemical properties to study and change
DNA molecules.



In genetic engineering, biologists make changes in the DNA code of a living
organism.


How do scientists make changes to


DNA?

Steps in DNA Identification


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.

Step 1: Copying DNA


Making Copies



Polymerase chain reaction (PCR)

is a technique that
allows biologists to
make copies

of DNA

from a very
small sample (a drop of blood).


A biologist makes short pieces of DNA (primers) that are
complementary to portions of the sequence.


DNA
two
strands are separated,
then
the
primers


bind to single
-
stranded
DNA, then

DNA
polymerase makes a copy of both strands


Polymerase Chain Reaction

DNA heated to
separate strands

PCR cycles

DNA copies

1

2

3

4

5 etc.

1

2

4

8

16 etc.

Polymerase Chain Reaction (PCR)

DNA polymerase adds
complementary strand

DNA fragment to
be copied

Step 2: Cutting DNA


Cutting DNA



Most DNA molecules are too large to be analyzed, so
biologists cut them into smaller fragments using
restriction enzymes.

Restriction Enzymes


= Bacterial
enzymes (endonucleases) that cut DNA at
specific
restriction
sites =
palindromes


Will cut
any

DNA the same
way

ZIG
-
ZAG


CUT

Recognition sequences

ZIG
-
ZAG


CUT

Cutting DNA


Restriction enzymes are used to cut human DNA into
fragments containing genes and repeats.



How many restriction sites are in the noncoding
region depends on each person’s DNA



Therefore each person’s DNA can be cut into
different size pieces and then separated


Cutting DNA

Step 3: Sorting DNA by Size


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.


When the power is turned on,
the negatively
-
charged DNA
molecules move toward the
positive end of the gel.

Gel Electrophoresis

DNA plus restriction enzyme

Mixture of DNA
fragments

Gel

Power
source

Longer
fragments

Shorter
fragments

Gel Electrophoresis


First, restriction
enzymes cut DNA
into fragments.


The DNA
fragments are
poured into wells
on a gel.

DNA plus restriction
enzyme

Mixture of DNA
fragments

Gel

Gel Electrophoresis

Gel Electrophoresis


An electric voltage
is applied to the
gel. This moves the
DNA fragments
across the gel.


The smaller the
DNA fragment, the
faster and farther it
will move across
the gel.

Power
source

Gel Electrophoresis

Gel Electrophoresis


Based on size, the
DNA fragments
make a pattern of
bands on the gel.


These bands can
then be compared
with other samples
of DNA.

Gel Electrophoresis

Gel Electrophoresis


Gel electrophoresis can be used to compare
the genomes of different organisms or
different individuals.


It can also be used to locate and identify one
particular gene in an individual's genome.

Recombinant DNA


DNA technology also
makes
it possible to
take a gene from one
organism and
insert

it
into
the DNA of
another organism.


Such DNA
molecules
produced by
genetic
engineering

are
called
recombinant DNA.

Cell Transformation
-

During transformation, a cell
takes in DNA from outside the cell. (Remember GRIFFITH?)
The external DNA becomes a component of the cell's DNA.

Recombinant DNA

Host Cell DNA

Target gene

Modified Host Cell DNA

Transforming

Bacteria



Foreign (engineered) DNA is
first joined to a small,
circular DNA molecule
known as a
plasmid
.


Plasmids are found naturally
in some bacteria and have
been very useful for DNA
transfer.


The plasmid has a
genetic

marker

a gene that makes
it possible to distinguish
bacteria that carry the
plasmid (and the foreign
DNA) from those that don't.

Transforming Bacteria



Recombinant DNA

Gene for human
growth hormone

Gene for human
growth hormone

Human Cell

Bacteria cell

Bacterial
chromosome

Plasmid

Sticky
ends

DNA
recombination

Bacteria cell
containing gene for
human growth
hormone

DNA
insertion


Transforming Cells


How can you tell if a transformation experiment
has been successful?

pGlo


Transgenic Organisms

An organism described as
transgenic
, contains genes from
other species.

Transgenic Microorganisms


Transgenic bacteria produce
important substances useful for
health and industry. Transgenic
bacteria have been used to
produce:


insulin


growth hormone


clotting factor

Transgenic Animals


Transgenic animals have been used
to study genes and to improve the
food supply.


Mice have been produced with
human genes that make their
immune systems act similarly to
those of humans. This allows
scientists to study the effects of
diseases on the human immune
system.


Researchers are trying to produce
transgenic chickens that will be
resistant to the bacterial infections
that can cause food poisoning.

Transgenic Plants



Transgenic plants are
now an important part
of our food supply.


Many of these plants
contain a gene that
produces a natural
insecticide, so plants
don

t have to be
sprayed with
pesticides.

Gene Therapy



In gene therapy, an
absent or faulty gene is
replaced by a normal,
working gene.


The body can then
make the correct
protein or enzyme,
eliminating the cause
of the disorder.

Gene Therapy


Viruses are often used
because of their ability
to enter a cell

s DNA.


Virus particles are
modified so that they
cannot cause disease
.


Cystic Fibrosis,
hemophilia, diabetes,
cancer

Normal hemoglobin gene

Genetically engineered virus

Gene Therapy


The patient is then infected with the modified
virus particles, which should carry the gene
into cells to correct genetic defects.


Cloning


A
clone
is a
member of a
population of
genetically
identical cells
produced from a
single cell.


In 1997, Ian
Wilmut

cloned a
sheep called
Dolly.

Dolly and Bonnie

The Human Genome Project


Only about 2 percent codes for


proteins
-

only 20
-
25,000 genes


Biotechnology
companies are looking for
information that may help develop new drugs and
treatments for diseases.


A Breakthrough for Everyone! Data from publicly
supported research on the human genome have
been posted on the Internet


BIOINFORMATICS


Biology, computer science, information
technology


Organize databases: genes, proteins


Proteome = all of an organism’s proteins


Structures


Interactions


A
bundance

Ethical Issues in Human Genetics