Chapter 13 – Genetic Engineering


12 Δεκ 2012 (πριν από 5 χρόνια και 4 μήνες)

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Chapter 13


L2 Biology

Has Bonnie been bred by selective breeding?

Selective Breeding

Choose organisms with the desired traits
and breed them, so the next generation also
has those traits

Nearly all domesticated animals and crops

Luther Burbank (1849
1926) developed
>800 diff varieties of plants in his lifetime


Breed two dissimilar organisms

In plants

often results in better lines

hybrids are larger, stronger,

In animals

hybrids produced may be weaker and sterile


wolf x dog

weak wolf


horse x donkey

mule (sterile)

Horse x Donkey = Mule

Lion x Tiger = Liger


Breeding two organisms that are

very similar to produce offspring

with the desired traits.


dog breeds


might bring together two
individuals that carry bad recessive genes

many purebred dogs have genetic disorders
that mutts don’t get.

Increasing Variation

Induce mutations

the ultimate source of
genetic variations among a group of

Mutagens used

radiation and chemicals

Some organisms are formed that have more
desirable variations.

Producing new kinds of bacteria

Can expose millions of bacteria at one time
to radiation

increases chances of
producing a successful mutant.


bacteria that can digest oil have been
produced this way

Producing new kinds of plants:

Drugs that prevent chromosomal separation
in meiosis have been used to create plants
that have more than two sets of
chromosomes (2n). These are called
polyploid plants.


bananas, citrus fruit, strawberries, many
ornamental flowers

Diploid corn

Tetraploid corn

Manipulating DNA

tools of the
molecular biologist

DNA extraction

open the cells and
separate DNA from all the other cell parts.

Remember the kiwi lab?

Cutting DNA

Use restriction enzymes

each one cuts DNA at a

specific sequence of nucleotides.

This will make different

lengths of DNA

Separating DNA

Gel Electrophoresis

Place fragments at one end of a porous gel

use agarose gel

Apply an electric current

The DNA is
negatively charged and will travel toward the
positive end of the gel.

The larger pieces of DNA move slower, the
smaller ones faster.

Used to compare genomes of different
organisms or different individuals.

Also used to locate and identify one particular
gene out of an individual’s genome.

Click here for animation about
gel electrophoresis

Using the DNA Sequence

Sequence can be read, studied, and changed.

Techniques used to study DNA sequences:

Use DNA polymerase and the 4 DNA bases to
produce a new DNA strand complementary to
unknown strand

some of the bases are dyed.

labeled strands are then separated using gel
electrophoresis and the order of the bands tells the
DNA sequence of the unknown strand.

Cutting and Pasting

make recombinant DNA (DNA from
two different organisms).

Cut out the gene to be inserted, use same restriction
enzyme to cut the receiving DNA strand, attach the two
DNA strands

Making Copies

Polymerase Chain Reaction (PCR) is used
to make many copies of the same piece of
DNA like a photocopy machine makes
copies of papers.

This is useful if there is only a very small
sample of DNA available (as that found in a
small blood drop at a crime scene)

Cell Transformation

A cell takes in DNA from outside the cell
and that DNA then becomes part of the
cell’s DNA.


place DNA in the solution that
bacteria live in, and some of that DNA will
be taken in by the bacteria cells.

Bacteria Transformation using
Recombinant DNA

Cut a gene with a restriction enzyme out of a
human cell (ex

gene for insulin or growth
hormone work well)

Cut a bacterial plasmid using the same restriction
enzyme (DNA ends will be complementary)

Insert Human gene into bacterial plasmid

Insert plasmid back into bacterial cell

Bacteria will multiply, and all offspring will have
that gene

these bacteria will then follow the
directions of the human gene and make the protein
coded for (insulin or human growth hormone)

Transforming Plant Cells

Use bacterial plasmid to insert desired gene
into DNA of a plant

Transforming Animal Cells

Directly inject DNA into the nucleus of an egg

it will become part of the chromosomes.

Has been used to replace specific genes.

Glowing mouse cells in
embryos that were made
from sperm given the gene
for bioluminescence from

now all the cells

Applications of Genetic

Gene for luciferase was isolated from
fireflies and inserted into tobacco plants

they glowed!

Transgenic organisms

contain genes from
other species

A transgenic mouse,
which carries

a jellyfish gene,
glows green under

fluorescent light.

Transgenic Organisms


Make human proteins like insulin


52% of soybeans, 25% of corn in
US in year 2000. Some produce natural
insecticide, some resist weed
killers, may
soon be used to produce human antibodies;
rice with vitamin A.


with immune
systems like
humans; farm
animals that grow
faster and larger
with extra copies of
growth hormone
genes; animals with
leaner meat;
chickens resistant to
bacterial infections.



member of a population

of genetically identical cells

produced from a single cell.





mammal (sheep) cloned.

She got arthritis several years

earlier than most sheep

Died in 2003