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13 Changing the Living World
(In a nutshell) How can genetics be used to change
organisms?
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13-1 Changing the Living World
Selective Breeding
Selective Breeding
Selective breeding allows only those organisms
with desired characteristics to produce the next
generation.
Nearly all domestic animals and most crop plants
have been produced by selective breeding.
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Selective Breeding
Humans use selective breeding to pass
desired traits on to the next generation
of organisms.
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Selective Breeding
Hybridization
Hybridization is the crossing of dissimilar
individuals to bring together the best of both
organisms.
Hybrids, the individuals produced by such
crosses, are often hardier than either of the
parents.
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Selective Breeding
Inbreeding
Inbreeding is the continued breeding of
individuals with similar characteristics.
Inbreeding helps to ensure that the characteristics
that make each breed unique will be preserved.
Serious genetic problems can result from
excessive inbreeding.
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Increasing Variation
Breeders increase the genetic variation
in a population by inducing mutations.
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Increasing Variation
Mutations occur spontaneously, but breeders can
increase the mutation rate by using radiation and
chemicals.
Breeders can often produce a few mutants with
desirable characteristics that are not found in the
original population.
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Increasing Variation
Producing New Kinds of Bacteria
Introducing mutations has allowed scientists to
develop hundreds of useful bacterial strains,
including bacteria that can clean up oil spills.
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Increasing Variation
Producing New Kinds of Plants
Mutations in some plant cells produce cells that
have double or triple the normal number of
chromosomes.
This condition, known as polyploidy, produces new
species of plants that are often larger and stronger
than their diploid relatives.
Polyploidy in animals is usually fatal.
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13-1 Changing the Living World
The Tools of Molecular Biology
The Tools of Molecular Biology
How do scientists make changes to DNA?
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The Tools of Molecular Biology
Scientists use different techniques to:
extract DNA from cells
cut DNA into smaller pieces
identify the sequence of bases in a DNA molecule
make unlimited copies of DNA
In genetic engineering, biologists make changes
in the DNA code of a living organism.
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The Tools of Molecular Biology
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.
Cutting DNA
Most DNA molecules are too large to be analyzed,
so biologists cut them into smaller fragments using
restriction enzymes.
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The Tools of Molecular Biology
Each restriction enzyme cuts DNA at a specific
sequence of nucleotides.
Recognition sequences
DNA sequence
Restriction enzyme EcoR I cuts
the DNA into fragments
Sticky end
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The Tools of Molecular Biology
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.
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The Tools of Molecular Biology
Power
source
DNA plus restriction
enzyme
Longer
fragments
Mixture of
DNA
fragments
Gel
Gel Electrophoresis
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Shorter
fragments
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First, restriction
enzymes cut DNA
into fragments.
The Tools of Molecular Biology
DNA plus
restriction enzyme
The DNA
fragments are
poured into wells
Mixture of DNA
on a gel.
fragments
Gel Electrophoresis
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Gel
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An electric
voltage is applied
to the gel.
The smaller the
DNA fragment,
the faster and
farther it will
move across the
gel.
The Tools of Molecular Biology
Power
source
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The Tools of Molecular Biology
Power
source
Longer
fragments
Shorter
fragments
Gel Electrophoresis
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13-1 Changing the Living World
Using the DNA Sequence
Making Copies
Polymerase chain reaction (PCR) is a technique
that allows biologists to make copies of genes.
Small amounts of DNA can be multiplied making it
easier to analyze.
Made possible by an enzyme found in a bacterium
living in hot springs in Yellow Stone National Park.
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Using the DNA Sequence
Polymerase Chain Reaction (PCR)
DNA heated to
separate strands
DNA polymerase adds
complementary strand
DNA fragment
to be copied
PCR cycles 1
DNA copies 1
2
2
3
4
4
8
5 etc.
16 etc.
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13-1 Changing the Living World
Transgenic Organisms
Transgenic Organisms
An organism described as transgenic, contains
genes from other species.
Genetic engineering has spurred the growth of
biotechnology.
How do we make them? (specifically bacteria)
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13-1 Changing the Living World
Transforming Bacteria
Foreign 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.
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Transgenic Organisms
Transgenic Microorganisms
Transgenic bacteria produce important substances
useful for health and industry. Transgenic bacteria
have been used to produce:
• insulin
• growth hormone
• clotting factor
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13-1 Changing the Living World
Cloning
Dolly and Bonnie
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.
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13-1 Changing the Living World Cloning
Cloning Dolly
Donor Nucleus
Fused cell
Egg Cell
Embryo
Cloned
Lamb
Foster Mother
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Cloning
Cloning Dolly
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Cloning
Cloning Dolly
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13-1 Changing the Living World
Cloning
Cloning Dolly
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Cloning
Researchers hope cloning will enable them
to make copies of transgenic animals and
help save endangered species.
Studies suggest that cloned animals may
suffer from a number of genetic defects
and health problems.
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