Chapter 13 - Western High School

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Transcript Chapter 13 - Western High School

Chapter 13
Genetics and Biotechnology
13.1 Applied Genetics
Applied Genetics
 Selective breeding is used to produce organisms
with desired traits.
Dog breeds
 Hybridization
 Time consuming
 Expensive
 Inbreeding
 Two closely related organisms are bred to have the
desired traits and to eliminate the undesired ones in
future generations
 Advantage – desired traits are passed on
 Disadvantage – harmful recessive traits can
be passed on
 Increases the chance of homozygous
recessive offspring: if both parents carry the
recessive allele, the harmful trait likely will not
be eliminated.
Test Cross
 Involves breeding an organism that has the
unknown genotype with one that is
homozygous recessive for the desired trait.
 If the parent’s genotype is homozygous
dominant, all the offspring will have the
dominant phenotype; if it is heterozygous, the
offspring will show a 1:1 phenotypic ratio.
Section 13.2: DNA Technology
 Researchers use genetic engineering to
manipulate DNA
 Genetic engineering – technology that
involves manipulating the DNA of one
organism in order to insert exogenous DNA
(the DNA of another organism).
Example: GFP- green fluorescent protein
Some fish – neons may contain GFP
GFP – found in jellyfish
DNA Tools
 Genome: an organisms total DNA present in the
nucleus of each cell
 The Human Genome – can contain millions and
millions of nucleotides
 DNA tools can be used to manipulate DNA and to
isolate genes from the rest of the genome
 Restriction enzymes – proteins that recognize and
bind to specific DNA sequences and cleave the DNA
within that sequence
DNA Tools
 A restriction enzyme is also called an endonuclease
 It cuts the viral DNA into fragments after it enters the
 Restriction enzymes are used as powerful tools for
isolating specific genes or regions of the genome
 When the restriction enzyme cleaves genomic DNA,
it creates fragments of different sizes that are unique
to every individual
DNA Tools
 EcoRI – cuts DNA containing the sequence
 The end of the DNA fragments created by
EcoRI are called sticky ends because they
contain single-stranded DNA that is
 Figure 13.4 on page 364
 Sticky ends are important because they can
be joined together with other DNA fragments
that have complementary sticky ends
DNA Tools
 Not all restriction enzymes create sticky ends
 Some enzymes produce fragments
containing blunt ends
 Blunt ends do not have regions of singlestranded DNA and can join to any other DNA
fragment with blunt ends
DNA Tools
 Gel electrophoresis – an electric current is
used to separate the DNA fragments
according to the size of the fragment
 The smaller fragments move farther faster
 When the loaded gel is placed in an
electophoresis tank and the electric current is
turned on, the DNA fragments separate
 Page 365 – see Figure 13.5
Recombinant DNA Technology
 When DNA fragments have been separated
by gel electophoresis, fragments of a specific
size can be removed from the gel and
combined with DNA fragments from another
 This newly generated DNA molecule, with
DNA from different sources, is called
recombinant DNA.
Recombinant DNA Technology
 A carrier, called a vector, transfers the
recombinant DNA into a bacterial cell called
the host cell.
 Plasmids and viruses – commonly used as
 Plasmids – small, circular, double-stranded
DNA molecules that occur naturally in
bacteria and yeast cells – used as vectors
because they can be cut with restriction
Recombinant DNA Technology
 Figure 13.6 on page 366
 DNA ligase – an enzyme normally used by
cells for DNA repair and replication, joins the
two DNA fragments chemically (both sticky
and blunt ends)
 Once complete, recombinant plasmid DNA
molecules can be inserted into a host cell and
more can be made
Recombinant DNA Technology
 Gene cloning
To make large amounts of recombinant
plasmid DNA, bacterial cells are mixed with
recombinant plasmid DNA
This can happen through a process called
Figure 13.7 on page 367
After transformation occurs, replication of
bacteria results in a process called cloning
Recombinant DNA Technology
 DNA sequencing
The sequence of the DNA nucleotides of most
organisms is unknown
Knowing the sequences of an organism’s DNA
or of a cloned DNA fragment provides valuable
information for scientists
Can be used to:
predict function of a gene
To compare genes
Identify mutations or errors in sequence
Recombinant DNA Technology
 Figure 13.8 on page 368
 DNA can be sequenced using fluorescent-
tagged nucleotides
 Polymerase chain reaction – a process used
to make millions of copies of a specific region
of a DNA fragment
 PCR – extremely sensitive and can detect a
single DNA molecule in a sample and can
then be copied or amplified
 Figure 13.9 page 369 – steps of PCR
Steps of Polymerase Chain Reaction
 Step 1: DNA fragment to be copied, DNA
polymerase, four DNA nucleotides and two
short single-stranded pieces of DNA called
primers are placed in a tube
The primers are complementary to the ends of
the DNA fragment that will be copied and used
as starting points for DNA synthesis
PCR begins when the tube is heated
Steps of Polymerase Chain Reaction
 Step 2: Heat separates the two strands of the
template DNA fragment
When tube is cooled, the primers can bind to
each strand of the template DNA
Thermocycler – automated machine used to
cycle the tube containing all the components
used in PCR through hot and cold
Steps in Polymerase Chain Reaction
 Step 3: Each primer binds to one strand of
the DNA fragment
Once primers are bound, DNA polymerase
incorporates the correct nucleotides between
the two primers
 Process of heating, cooling, and nucleotide
incorporation is repeated 20 to 40 times =
millions of copies of original fragment
Used by researchers in labs, forensic scientists
and doctors
Genetic Engineering
Table 13.1 page 370
Restriction enzymes
Gel electophoresis
Recombinant DNA technology
Gene cloning
DNA sequencing
Polymerase chain reaction (PCR)
Procedures often include: cleavage by a restriction
enzyme, isolation of fragments, combination with
exogenous DNA, cloning or PCR and identification of
 The use of genetic engineering to find
solutions to problems
 Transgenic organisms: organisms that are
genetically engineered by inserting a gene
from another organism
 Transgenic organisms (plants, animals,
bacteria) are used for research, medical and
agricultural purposes
Transgenic Animals
 Mice, fruit flies, and roundworms widely used in
research labs around the world to study diseases and
develop ways to treat them
Some transgenic livestock have been produced to
improve the food supply and human health
Transgenic goats used to secrete a protein used to
prevent human blood from clotting during surgery
Transgenic chickens and turkeys are being produced
that are resistant to disease
Transgenic fish are engineered to grow faster
In future, may be used as a source of organs for
organ transplants.
 Transgenic plants: many species have been
genetically altered to be more resistant to insect or
viral pests
Examples: soybeans, corn, cotton, canola
Being tested: sweet potatoes, bananas(for vaccines)
Transgenic bacteria: Insulin, growth hormones and
substances that dissolve blood clots are made from
transgenic bacteria
Transgenic bacteria are also used to clean up oil spills,
decompose garbage and protect crops from frost