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13-1 Changing the Living World
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13-1 Changing the Living World
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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13-1 Changing the Living World
Selective Breeding
Humans use selective breeding to pass
desired traits on to the next generation
of organisms.
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13-1 Changing the Living World
Selective Breeding
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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13-1 Changing the Living World
Selective Breeding
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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13-1 Changing the Living World
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13-1 Changing the Living World
Increasing Variation
Breeders increase the genetic variation
in a population by inducing mutations.
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13-1 Changing the Living World
Increasing Variation
Mutations occur spontaneously, but breeders can
increase the mutation rate by using______________
_________________________.
Breeders can often produce a few mutants with
desirable characteristics that are not found in the
original population.
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13-1 Changing the Living World
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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13-1 Changing the Living World
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.
Except in the case of the Red Viscacha Rat
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13-2 Manipulating DNA
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13-2 Manipulating DNA
The Tools of Molecular Biology
Scientists use their knowledge of the
structure of DNA and its chemical
properties to study and change DNA
molecules.
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13-2 Manipulating DNA
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
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13-2 Manipulating DNA
The Tools of Molecular Biology
In_______________________, biologists make
changes in the DNA code of a living organism.
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13-2 Manipulating DNA
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.
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13-2 Manipulating DNA
The Tools of Molecular Biology
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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13-2 Manipulating DNA
The Tools of Molecular Biology
Each ________________________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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13-2 Manipulating DNA
The Tools of Molecular Biology
A restriction enzyme will cut a DNA sequence only if
it matches the sequence precisely.
Recognition sequences
DNA sequence
Restriction enzyme EcoR I cuts
the DNA into fragments
Sticky end
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13-2 Manipulating DNA
The Tools of Molecular Biology
Separating DNA
In___________________________, 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 negativelycharged DNA molecules move toward the positive
end of the gel.
Whoa! We did this!!!!!!
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13-2 Manipulating DNA
The Tools of Molecular Biology
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.
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13-2 Manipulating DNA
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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13-2 Manipulating DNA
First, restriction
enzymes cut DNA into
fragments.
The Tools of Molecular Biology
DNA plus
restriction enzyme
The DNA fragments
are poured into wells
on a gel.
Mixture of DNA
fragments
Gel Electrophoresis
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Gel
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13-2 Manipulating DNA
The Tools of Molecular Biology
Power
source
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.
Gel Electrophoresis
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13-2 Manipulating DNA
The Tools of Molecular Biology
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.
Longer
fragments
Shorter
fragments
Gel Electrophoresis
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13-2 Manipulating DNA
Using the DNA Sequence
Using the DNA Sequence
Knowing the sequence of an organism’s DNA
allows researchers to study specific genes, to
compare them with the genes of other organisms,
and to try to discover the functions of different
genes and gene combinations.
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13-2 Manipulating DNA
Using the DNA Sequence
Reading the Sequence
In DNA sequencing, a complementary DNA strand
is made using a small proportion of fluorescently
labeled nucleotides.
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13-2 Manipulating DNA
DNA
Sequencing
Using the DNA Sequence
DNA strand with
unknown base
sequence
Dye molecules
DNA fragments
synthesized
using unknown
strand as a
template
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13-2 Manipulating DNA
Using the DNA Sequence
Each time a labeled nucleotide is added, it stops the
process of replication, producing a short color-coded
DNA fragment.
When the mixture of fragments is separated on a gel,
the DNA sequence can be read.
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13-2 Manipulating DNA
Using the DNA Sequence
Base sequence
as “read” from
the order of the
dye bands on
the gel from
bottom to top:
TGCAC
Electrophoresis gel
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13-2 Manipulating DNA
Using the DNA Sequence
Cutting and Pasting
Short sequences of DNA can be assembled using
DNA synthesizers.
“Synthetic” sequences can be joined to “natural”
sequences using enzymes that splice DNA
together.
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13-2 Manipulating DNA
Using the DNA Sequence
These enzymes also 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.
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13-2 Manipulating DNA
Using the DNA Sequence
Making Copies
________________________________________
is a technique that allows biologists to make copies
of genes.
A biologist adds short pieces of DNA that are
complementary to portions of the sequence.
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13-2 Manipulating DNA
Using the DNA Sequence
DNA is heated to separate its two strands, then cooled to allow
the primers to bind to single-stranded DNA.
DNA polymerase starts making copies of the region between
the primers.
• PCR song:
http://www.youtube.com/watch?v=7uafUVNkuzg
• DNA Song: http://www.youtube.com/watch?v=bF2QalUj1Y
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13-2 Manipulating DNA
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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