Interest Grabber
Section 13-1
A New Breed
The tomatoes in your salad and the dog in your backyard are a result of
selective breeding. Over thousands of years, humans have developed
breeds of animals and plants that have desirable characteristics. How do
breeders predict the results of crossing individuals with different traits?
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Section:
Interest Grabber continued
Section 13-1
1. Think of two very different breeds of dogs that are familiar to you. On a
sheet of paper, construct a table that has the following three heads: the
name of each of the two dog breeds, and “Cross-Breed.
2. The rows of the table should be labeled with characteristics found in
both breeds of dogs. Examples might include size, color, type of coat,
intelligence, aggression, and so on.
3. Fill in the column for each of the two dog breeds. In the column labeled
“Cross-Breed,” write in the characteristic you would expect to see in a
cross between the two breeds you have selected.
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Section:
Section Outline
Section 13-1
13–1
Changing the Living World
A. Selective Breeding
1. Hybridization
2. Inbreeding
B. Increasing Variation
1. Producing New Kinds of Bacteria
2. Producing New Kinds of Plants
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Section: Section:
Concept Map
Section 13-1
Selective
Breeding
consists of
Inbreeding
Hybridization
which crosses
which crosses
Similar
organisms
Dissimilar
organisms
Organism
breed A
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Section:
for
example
for
example
Organism
breed B
Organism
breed A
which
which
Retains desired
characteristics
Combines desired
characteristics
Interest Grabber
Section 13-2
The Smallest Scissors in the World
Have you ever used your word processor’s Search function? You can
specify a sequence of letters, whether it is a sentence, a word, or
nonsense, and the program scrolls rapidly through your document,
finding every occurrence of that sequence. How might such a function
be helpful to a molecular biologist who needs to “search” DNA for the
right place to divide it into pieces?
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Section:
Interest Grabber continued
Section 13-2
1. Copy the following series of DNA nucleotides onto a sheet of paper.
GTACTAGGTTAACTGTACTATCGTTAACGTAAGCTACGTTAACCTA
2. Look carefully at the series, and find this sequence of letters: GTTAAC.
It may appear more than once.
3. When you find it, divide the sequence in half with a mark of your pencil.
You will divide it between the T and the A. This produces short segments
of DNA. How many occurrences of the sequence GTTAAC can you find?
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Section:
Section Outline
Section 13-2
13–2
Manipulating DNA
A. The Tools of Molecular Biology
1. DNA Extraction
2. Cutting DNA
3. Separating DNA
B. Using the DNA Sequence
1. Reading the Sequence
2. Cutting and Pasting
3. Making Copies
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Section:
Restriction Enzymes
Section 13-2
Recognition sequences
DNA sequence
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Section:
Restriction Enzymes
Section 13-2
Recognition sequences
DNA sequence
Restriction enzyme
EcoRI cuts the DNA
into fragments.
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Section:
Sticky end
Figure 13-6 Gel Electrophoresis
Section 13-2
Power
source
DNA plus restriction
enzyme
Longer
fragments
Shorter
fragments
Mixture of DNA
fragments
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Section:
Gel
Figure 13-7 DNA Sequencing
Section 13-2
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Section:
Figure 13-8 PCR
Section 13-2
DNA polymerase adds
complementary strand
DNA heated to
separate strands
DNA fragment
to be copied
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Section:
PCR
cycles 1
2
3
4
5 etc.
DNA
copies 1
2
4
8
16 etc.
Interest Grabber
Section 13-3
Sneaking In
You probably have heard of computer viruses. Once inside a
computer, these programs follow their original instructions and
override instructions already in the host computer. Scientists use
small “packages” of DNA to sneak a new gene into a cell, much as a
computer virus sneaks into a computer.
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Section:
Interest Grabber continued
Section 13-3
1. Computer viruses enter a computer attached to some other file.
What are some ways that a file can be added to a computer’s
memory?
2. Why would a person download a virus program?
3. If scientists want to get some DNA into a cell, such as a bacterial
cell, to what sort of molecule might they attach the DNA?
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Section:
Section Outline
Section 13-3
13–3
Cell Transformation
A. Transforming Bacteria
B. Transforming Plant Cells
C. Transforming Animal Cells
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Section:
Knockout Genes
Section 13-3
Recombinant DNA
Flanking sequences
match host
Host Cell DNA
Target gene
Recombinant DNA replaces
target gene
Modified Host Cell DNA
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Section:
Figure 13-9 Making Recombinant DNA
Section 13-3
Recombinant
DNA
Gene for human
growth hormone
Gene for human
growth hormone
Human Cell
Sticky
ends
DNA
recombination
DNA
insertion
Bacterial Cell
Bacterial
chromosome
Plasmid
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Section:
Bacterial cell for
containing gene for
human growth hormone
Figure 13-10 Plant Cell Transformation
Section 13-3
Agrobacterium
tumefaciens
Gene to be
transferred
Cellular
DNA
Recombinant
plasmid
Inside plant cell,
Agrobacterium inserts part of
its DNA into host cell
chromosome
Plant cell colonies
Transformed bacteria introduce
plasmids into plant cells
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Section:
Complete plant is
generated from
transformed cell
Interest Grabber
Section 13-4
The Good With the Bad
The manipulation of DNA allows scientists to do some interesting
things. Scientists have developed many transgenic organisms, which
are organisms that contain genes from other organisms. Recently,
scientists have removed a gene for green fluorescent protein from a
jellyfish and tried to insert it into a monkey.
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Section:
Interest Grabber continued
Section 13-4
1. 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?
2. 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?
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Section:
Section Outline
Section 13-4
13–4
Applications of Genetic Engineering
A. Transgenic Organisms
1. Transgenic Microorganisms
2. Transgenic Animals
3. Transgenic Plants
B. Cloning
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Section:
Flowchart
Section 13-4
Cloning
A body cell is taken from a donor animal.
An egg cell is taken from a donor animal.
The nucleus is removed from the egg.
The body cell and egg are fused by electric shock.
The fused cell begins dividing, becoming an embryo.
The embryo is implanted into the uterus of a foster mother.
The embryo develops into a cloned animal.
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Section:
Figure 13-13 Cloning of the First Mammal
Section 13-4
A donor cell is taken from
a sheep’s udder.
Donor
Nucleus
These two cells are fused
using an electric shock.
Fused Cell
Egg Cell
The nucleus of the
egg cell is removed.
An egg cell is taken
from an adult
female sheep.
Embryo
Cloned Lamb
The embryo
develops normally
into a lamb—Dolly
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Section:
The fused cell
begins dividing
normally.
Foster
Mother
The embryo is placed
in the uterus of a foster
mother.
Video
Gene Transfer
Click the image to play the video segment.
Go Online
Links from the authors on genetically modified foods
Interactive test
For links on recombinant DNA, go to www.SciLinks.org and enter the
Web Code as follows: cbn-4132.
For links on genetic engineering, go to www.SciLinks.org and enter the
Web Code as follows: cbn-4134.
Interest Grabber Answers
1. Think of two very different breeds of dogs that are familiar to you. On a
sheet of paper, construct a table that has the following three heads: the
name of each of the two dog breeds, and “Cross-Breed.
Encourage students to refer only to breeds with which they are familiar.
2. The rows of the table should be labeled with characteristics found in both
breeds of dogs. Examples might include size, color, type of coat,
intelligence, aggression, and so on.
Additional traits might include shape of ears, shape of muzzle (pointed or
square), or length of legs with respect to body.
3. Fill in the column for each of the two dog breeds. In the column labeled
“Cross-Breed,” write in the characteristic you would expect to see in a
cross between the two breeds you have selected.
Students will likely assume that traits of the cross-breed are intermediate
between those of the two parent breeds.
Interest Grabber Answers
1. Copy the following series of DNA nucleotides onto a sheet of paper.
GTACTAGGTTAACTGTACTATCGTTAACGTAAGCTACGTTAACCTA
2. Look carefully at the series, and find this sequence of letters: GTTAAC. It
may appear more than once.
1–2: Remind students to check their copies for accuracy before they begin
the next step.
3. When you find it, divide the sequence in half with a mark of your pencil.
You will divide it between the T and the A. This produces short segments of
DNA. How many occurrences of the sequence GTTAAC can you find?
Students should find three occurrences of the sequence:
GTACTAGGTTAACTGTACTATCGTTAACGTAAGCTACGTTAACCTA
Interest Grabber Answers
1. Computer viruses enter a computer attached to some other file. What are
some ways that a file can be added to a computer’s memory?
A file can be downloaded from a diskette, a CD, or the Internet.
2. Why would a person download a virus program?
The computer user would not willingly download a virus but would
download a program that was useful.
3. If scientists want to get some DNA into a cell, such as a bacterial cell, to
what sort of molecule might they attach the DNA?
Possible answers: a useful protein or a strand of DNA that the cell would
recognize and accept
Interest Grabber Answers
1. 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?
Students may say that a mouse with a humanlike immune system would be
a good laboratory model for immune research.
2. 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 might disrupt normal balances in ecosystems and
could breed with natural populations, changing them.
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