Genetic Engineering

triteritzyΒιοτεχνολογία

14 Δεκ 2012 (πριν από 4 χρόνια και 8 μήνες)

194 εμφανίσεις

DNA Technology &

Genetic Engineering

Georgia Performance Standards:



Examine the use of DNA technology in


forensics, medicine, and agriculture.




Essential Questions:




How are genetically modified plants and animals made
and used in medicine and agriculture?



How is DNA technology applied to solving problems?


Selective Breeding


Selective Breeding
-

a method of
improving a species by allowing only those
individual organisms with desired
characteristics to produce to the next
generation


Hybridization


Inbreeding


Hybridization:


Hybridization

is a breeding technique that
involves
crossing different individuals

to
bring together the best traits of both
organisms



Ex: combining the disease resistance of one
plant with the food
-
producing capacity of
another produces a hardier plant that
increased food supply.

Inbreeding



Inbreeding

is the continued breeding of
individuals with
similar characteristics
.



Used to
maintain desired characteristics



Inbreeding helps to ensure that the
characteristics that make each breed unique will
be preserved.



Risks:

Most of the members of a breed are
genetically similar and genetic defects can arise.


which crosses

consists of

Selective Breeding

for
example

for
example

Organism
breed A

Organism
breed A

Organism
breed B

Retains desired
characteristics

Combines desired
characteristics

which

which crosses

which

Concept Map

Inbreeding

Hybridization

Similar

Organisms

Dissimilar

Organisms

Increasing Variation


Sometimes breeders want more variation
than exists in nature.






Breeders can
increase the genetic
variation

in a population
by inducing
mutations
, which are the ultimate source
of genetic variability.


Radiation


Chemicals

Plant Breeding



Drugs used in plant breeding sometimes cause
plants to produce cells that have double or triple
the normal number of chromosomes.



Plants grown from such cells are called
polyploid

because they have many sets of
chromosomes.



Polyploidy produces larger and stronger
plants, which increase the food supply for
humans.

Checkpoint Questions:

1.
Give one example of selective breeding.


2.
Relate genetic variation and mutations to each
other.


3. How might a breeder induce mutations?


4. What is polyploidy?


5. Suggest ways that plants could be altered to
improve the world’s food supply.

Manipulating DNA:



How are changes made to DNA?





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




Different techniques are used:


to extract DNA from cells


to cut DNA into smaller pieces


to identify the sequence of bases in a DNA molecule


to make unlimited copies of DNA.

Genetic engineering


Genetic Engineering

-

making changes in
the DNA code of a living organism.


Process:


DNA extraction


Cutting DNA


Separating DNA


Reading the sequence


Cutting and pasting


Making copies


Molecular

Biology

DNA Extraction


How do biologists get DNA out of a cell?




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.

Cutting DNA



DNA molecules from most organisms are
much too large to be analyzed, so
biologists cut them precisely into smaller
fragments using restriction enzymes.



Restriction enzymes

cut DNA at a
specific sequence of nucleotides.


Very precise

Restriction Enzymes Cut DNA


This drawing shows how
restriction enzymes are
used to edit DNA.



The restriction enzyme
Eco
RI, for example, finds
the sequence CTTAAG
on DNA.



Then, the enzyme cuts
the molecule at each
occurrence of CTTAAG.



Different restriction
enzymes recognize and
cut different sequences of
nucleotides on DNA
molecules.

VIDEO

Separating DNA



In
gel electrophoresis
, a
mixture of DNA fragments
is placed at one end of a
porous gel, and an electric
voltage is applied to the
gel.



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



The smaller the DNA
fragment, the faster it
moves.



Uses:


Comparing
genomes of
different organisms
or individuals.



Locating and
identifying one
particular gene out
of the millions of
genes in an
individual’s
genome.


DNA plus
restriction
enzyme

Mixture of
DNA
fragments

Gel

Power
source

Longer
fragments

Shorter
fragments

Gel Electrophoresis Separates DNA

Making Copies


In order to study
genes, biologists
often need to make
many copies of a
particular gene.



A technique known as
polymerase chain
reaction (PCR)

allows biologists to
make copies of DNA.


PCR Process:


1. DNA is heated to
separate strands


2. DNA is cooled to
allow primers to
bind


3. DNA polymerase
copies the strands


PCR:

Polymerase Chain

Reaction makes
copies of DNA

DNA fingerprinting


The pattern that results from gel
electrophoresis is known as as DNA finger
print.



The more similar the DNA fingerprints
of two organisms, the more recently
they shared a common ancestor.

DNA fingerprinting


Analysis of sections of DNA that have little
or no known function, but vary widely from
one individual to another, in order to
identify individuals



The reliability of DNA evidence has
helped convict criminals as well as
overturn many convictions.




-

The technicians
place a DNA
fingerprint from a
known person
next to a DNA
fingerprint found
at the scene of
the crime.


-

If the DNA
fingerprints
match, the
person can be
placed at the
scene of the
crime.

-
It is easy to see in this
example that daughter 2 is the
child from the mother’s
previous marriage and son 2 is
adopted.


-
You can see that both
daughter 1 and son 1 share
RFLPs with both the mom and
dad (colored blue and yellow
respectively), while daughter 2
has RFLPs of the mom but not
the dad, and son 2 does not
have RFLPs from either
parent.


-

Even if the RFLPs were not
color coded, you could still
distinguish the parents of the
children by looking at the
position of the bands in the
agarose gel. In reality, all of the
bands look the same and only
the positions are different.

Genetics and Biotechnology


To understand how DNA is sequenced, scientists mix an
unknown DNA fragment, DNA polymerase, and the four
nucleotides

A, C, G, T in a tube.

13.2 DNA Technology

Chapter
13

Genetics and Biotechnology


Each nucleotide is
tagged with a
different color of
fluorescent dye.


Every time a
modified
fluorescent
-
tagged
nucleotide is

incorporated into the newly synthesized strand,

the reaction stops.

13.2 DNA Technology

Chapter
13

Genetics and Biotechnology


The sequencing reaction is complete when the
tagged DNA fragments are separated by gel
electrophoresis.

13.2 DNA Technology

Chapter
13

Reading a DNA Sequence

Figure 22.3

Deriving a DNA Sequence

Figure 22.4

Checkpoint Questions:

1.
Describe the process scientists use to manipulate DNA.


2. Why might a scientist want to know the sequence of a
DNA molecule?


3. How does gel electrophoresis work?


4. Which technique can be used to make multiple copies of
a gene? What are the basic steps in this procedure?


5. How is genetic engineering like computer programming?

Cell Transformation


During
Cell Transformation
, a cell takes in
DNA from outside the cell.


Plant and animal



This external DNA becomes a part of the
cell’s DNA.


One way to make recombinant DNA is to
insert a human gene into bacterial DNA.


The new combination of genes is then
returned to a bacterial cell, and the bacteria
can produce the human protein.


video


Cutting and Pasting




Enzymes make it possible to take a gene
from one organism and attach it to the
DNA of another organism.



Such DNA molecules are sometimes
called
recombinant DNA

because they
are
produced by combining DNA from
different sources
.

Transforming Bacteria


Recombinant DNA is used.



The foreign DNA is first joined to a small,
circular DNA molecule

known as a
plasmid
.


Plasmids have a DNA sequence that serves
as a bacterial origin of replication.


Plasmids have a
genetic marker

a gene
that makes it possible to distinguish bacteria
that carry the plasmid from those that don’t.

Transforming Bacteria

Plant Cell Transformation



Recombinant plasmids can be used to infect
plant cells.



DNA can also be injected directly into some
plant cells.



Cells transformed by either procedure can be
cultured to produce adult plants.








Recombinant
plasmid

Gene to be
transferred

Agrobacterium
tumefaciens

Cellular
DNA

Transformed bacteria
introduce plasmids into
plant cells

Plant cell
colonies

Complete plant is
generated from
transformed cell

Inside plant cell,
Agrobacterium
inserts
part of its DNA into host
cell chromosome

Plant Cell Transformation

Checkpoint Questions:

1.
What is transformation?


2.
How can you tell if a transformation experiment
has been successful?

3. How are genetic markers related to
transformation?


4. What are two features that make plasmids
useful for transforming cells?


5. Compare the transformation of a prokaryotic cell
with the transformation of a eukaryotic cell.

Applications of Genetic Engineering


Scientists have developed many
transgenic organisms, which are
organisms that contain genes from other
organisms.


scientists have removed a gene for green
fluorescent protein from a jellyfish and tried to
insert it into a monkey.



Applications of Genetic Engineering


Transgenic animals are often used in
research.



What might be the benefit to medical research of a
mouse whose immune system is genetically altered
to mimic some aspect of the human immune
system?



Transgenic plants and animals may have
increased value as food sources.


What might happen to native species if transgenic
animals or plants were released into the wild?



Transgenic Organisms:


The universal nature of genetic mechanisms
makes it possible to construct organisms that
are
transgenic
, meaning that they contain
genes from other organisms.



A gene from one organism can be inserted
into cells from another organism.




These transformed cells can then be used to
grow new organisms.

Transgenic Bacteria or Yeast:



Transgenic bacteria reproduce rapidly and
are easy to grow.



Therefore they now produce a host of
important substances useful for health and
industry.


human insulin, growth hormone, and
clotting factor


Transgenic Animals:


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


Strains of mice


produced with human genes that make their immune
systems act similarly to those of humans.


study the effects of diseases on the human immune
system.



Transgenic livestock



produced with extra copies of growth hormone genes.


such animals grow faster and produce meat that is less
fatty than that from ordinary animals.



Transgenic chickens



resistant to the bacterial infections that sometimes
cause food poisoning.



Transgenic Plants:


Transgenic plants help
to increase our food
supply.



Genes produce a natural
insecticide (this avoids
synthetic pesticide use).



Genes that enable them
to resist weed
-
killing
chemicals (allows farmers
to grow more food by
controlling weeds.



Human antibodies
that can be used to
fight disease;



Plastics that can now
be produced only
from petroleum



Foods that are
resistant to rot and
spoilage.


Cloning:


A
clone

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



Cloned colonies of bacteria and other
microorganisms are easy to grow, but this
is not always true of multicellular
organisms, especially animals.

Cloning:


Clones are used for medical and
scientific value, but also causes ethical
issues.



In 1997, Scottish scientist Ian Wilmut
stunned biologists by announcing that he
had cloned a sheep


Cloning

A body cell is taken from a donor animal.

An egg cell is taken from a donor animal.

The fused cell begins dividing, becoming an embryo.

The nucleus is removed from the egg.

The body cell and egg are fused by electric shock.

The embryo is implanted into the uterus of a foster mother.

The embryo develops into a cloned animal.

A donor cell is taken from
a sheep’s udder.

Donor
Nucleus

These two cells are fused
using an electric shock.

Fused Cell

The fused cell
begins dividing
normally.

Embryo

The embryo is placed
in the uterus of a foster
mother.

Foster
Mother

The embryo
develops normally
into a lamb

Dolly

Cloned Lamb

Egg Cell

An egg cell is taken
from an adult
female sheep.

The nucleus of the
egg cell is removed.

Section 13
-
4

Cloning of the First Mammal

Go to
Section:

Checkpoint Questions:

1. List one practical application for each of the
following: transgenic bacteria, transgenic
animals, transgenic plants.


2. What is a transgenic organism?


3. What basic steps were followed to produce
Dolly?


4. List reasons you would or would not be
concerned about eating genetically modified
food.

The Human Genome Project:




The Human Genome Project is an attempt
to sequence all human DNA.



VIDEO

Gene Therapy


Curing genetic disorders by gene therapy.



Gene therapy

is the process of changing the
gene that causes a genetic disorder.






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




This way, the body can make the correct protein
or enzyme it needs, which eliminates the cause
of the disorder.

Normal hemoglobin gene

Bone
marrow cell

Chromosomes

Genetically engineered virus

Nucleus

Bone
marrow

Section 14
-
3

Figure 14
-
21 Gene Therapy

Go to
Section:

Checkpoint Questions:

1.
What is the Human Genome Project?


2.

Describe how gene therapy works.


3.

Name two common uses for DNA testing.


4.

Describe how molecular biologists identify genes in
sequences of DNA.


5.

Do you think it should be legal for people to use genetic
engineering to affect their children’s characteristics?
Give reasons for your answer.