Chapter 13 Genetic Engineering - nvohl

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12 Δεκ 2012 (πριν από 4 χρόνια και 8 μήνες)

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Chapter 13


Genetic Engineering


Changing the Living World

Selective Breeding


Humans use
selective breeding
, which
takes advantage of naturally occurring
genetic variations.


Domestic animals


Farm animals


Crop plants


Pass
desired traits

to the next generation

Hybredization


Luther Burbank may have been the greatest
selective breeder of all time (1849


1926)


Used
Hybredization

crossing dissimilar
individuals to bring out the best in each


Combined the disease resistance of one plant
with the food
-
producing capacity of another


The result was a new line of plants that allowed
farmers to increase food production

Inbreeding


The continued
breeding
of individuals with
similar characteristics


Breeds of dogs such as beagles and poodles


Risks


Chance that
two recessive alleles

form a
genetic defect


Joint problems with German shepherds for example


Increasing Variation


Selective breeding is possible because of
the
wide variation

found in natural
populations


Breeders increase the variation by
inducing
mutations

(mutations are the cause of
variations)


With luck over a number of attempts
desirable traits may be found.

Increasing Variation 2


Because of the small size of bacteria,
radiation or chemical treatment may
produce some of the bacteria with useful
characteristics.


Bacteria that digest oil


Bacteria that produce hydrogen


Increasing Variation 3


Producing new kinds of plants


Prevent chromosomal separation


Sometimes produce cells that have two to three
times the number of chromosomes


Called
polyploidy

the extra chromosomes in
plants sometimes make them larger and
stronger.


Polyploidy is fatal in animals

Manipulating DNA


Scientists have broken the DNA code


They study the structure of DNA and its
chemical properties.


Techniques are used to extract DNA from cells
and cut it into smaller pieces and identify the
sequence of bases in a DNA molecule and
make unlimited copies.


Manipulating DNA


Tools


DNA extraction



chemicals can separate the
DNA from other cell parts.


Cutting DNA



Restriction enzymes

are
known and each one cuts DNA at a specific
sequence of nucleotides.



DNA fragments

can be separated using
gel
electrophoresis.

A DNA fragment is placed at
one end of a porous gel, and voltage applied.
DNA molecules, which are negatively charged
move to the positive end of he gel.


The sequence can then be read.


Applications of Genetic
Engineering


Transgenic Organisms


It is possible to
construct organisms that are
transgenic,
meaning that they contain genes from other
species. The transformed cells grow new
organisms.


Transgenic microorganisms


transgenic
bacteria now produce substances that form
proteins cheaply and in great quantities.


ie. Insulin, growth hormone, and clotting factor

Cloning


A
clone

is a member of a population of
genetically identical cells produced from a
single cell.