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B3: New Genes for Old
Selective breeding Genetic Engineering
Selective breeding is the traditional method for Genetic engineering is a faster way, which
improving crops and livestock, such as transplants genes for a desired characteristic
increasing disease resistance or milk yield. into an organism. However, genetic
engineering offers many potential benefits but
carries the risk of unexpected harmful effects
These are the steps in selective breeding: Some examples why genetic engineering is used:
1. Decide which characteristics are important
2. Choose parents that show these characteristics
3. Select the best offspring from parents to breed the next
4. Repeat the process continuously
Some examples why selective breeding is used:
Genetic engineering has some potential advantages, such as being
able to produce organisms with desired features quickly.
Some people are concerned about the health risk of genetically
modified food. Others think it is wrong to create new life forms, or to
move genes between different species, especially if this causes harm.
Cross breeding is commonly involved which reduces the gene pool.
The number of alleles decreases; meaning there is less variation.
Cross-breeding increases the chance harmful recessive characteristics…read more

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Study this
Genetic engineering continued
Principles of genetic
When the organism engineering:
replicates, the Remember the gene
contains all genetic Click to
gene replicates, making a new protein
1. The gene for a desired characteristic is
e.g human information 2 recap what
The gene for a
selected e.g the human insulin gene. order these 3
desired steps come
2. The desired gene is isolated is
and taken out 1 in 4
selected e.g
gene an enzyme that cuts through
is inserted the DNA
the human
into in precise
the genome of places. insulin gene.
another organism e.g
3.bacteria cell. is inserted into the genome of
The gene
another organism e.g bacteria cell.
The desired gene is isolated and
4. When the organism replicates, the gene
taken out using an enzyme that cuts
replicates, through
making the
a new
DNA protein
strands e.g human
in precise
insulin. places.…read more

Slide 3

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Gene therapy
1. Doing research to find Using an
the gene involved in enzyme
the genetic disorder
This is only done to body
cells, not sex cells so these
genes wont be passed on to
offspring; it's illegal. Children
inherit their parent's faulty
Problems in the process
The main difficulty is usually the last step. Here are some of Different methods
the problems: Different methods are used to get the alleles into the
· The alleles may not go into every target cell patient's cells, including:
· The alleles may join with the chromosomes in random · Using fat droplets in nose sprays
places, so they do not work properly · Using cold viruses that are modified to carry the allele -
· Treated cells may be replaced naturally by the patient's the viruses go into the cells and infect them
own untreated cells. · The direct injection of DNA…read more


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