Download File - Hope Christian College Parent and Student Portal

Human
awareness



M16.1 Know that the DNA can be extracted
from cells
Genetic engineering and /or genetic
modification have been made possible by
isolating and manipulating genes extracted
from the DNA of species.
Genetic engineering means taking genes from
one organism and putting them into another to
create a modified gene or altering them and
putting them back into the original organism in
an altered state.

Other uses of genetic engineering are:
 Producing other proteins like vaccines
 Improving plants in terms of pest
resistant crops
 Improving animals like better wool,
more milk yield, improved meat etc
 Locating a gene of interest on the
chromosome
 Using enzymes to isolate
 Sequencing the gene to determine the
structure
 Inserting the gene into cells of the
target organism
 Growing the transformed cells into a
complete organism
Restriction enzymes are the
tools used to cut DNA in
various places.
• Found in bacteria
• Different species=different
enzymes
• Some work at boiling
point of water
• 1000 types known




IDENTIFYING AND ISOLATING THE
RIGHT GENE:
Once DNA is extracted and isolated from
nuclear proteins
restriction enzymes cut DNA into smaller
fragments ( these enzymes are found in
bacteria)
to isolate the specific gene in question two
methods are used:









must know a short sequence of nucleotides in a gene
if you know the protein for which the gene codes, you know
the amino acid sequence and should be able to deduce the
nucleotides
a short segment of a single strand of DNA or RNA with a
sequence of bases that is complimentary to part of the
required genes is selected
this is radioactively labelled and mixed with the double
stranded DNA fragments that contain the gene
the solution is heated and separated
on cooling, some of the probe molecules will bind to the
DNA fragments containing the specific complimentary base
sequence and identifies and locates the gene
DNA ligase that you remember helps seal the breaks in
DNA during replication, is used to form the recombinant
DNA
By inserting the DNA into a host organism it is possible to
make multiple copies of the required gene- this is then the
cloning process addressed next
See page 44 Essentials text




Cloning Genes:
to clone genes that have already been identified
and isolated, involves bacteria
as stated, bacteria have little circles of DNA
called plasmids
these are separated from the bacteria
Chromosomes




plasmids can be removed and cut with special
restriction enzymes
once cut, you end up with short sticky ended
bits of DNA…which can then attach to other
strands of DNA …as long as the ends have
complimentary nucleotides
This means that biologists can use a certain
enzyme to cut the plasmid at a particular point
and insert a gene of interest which has been
identified in humans and also removed using a
probe or antibody method.
The DNA is stuck together using ligase and the
plasmids reform into rings






they are mixed with bacterial cells which take
them up quite readily
Bacteria reproduces rapidly and each time it
reproduces, this particular gene will be copied--gene cloning
this is a way to produce bio-chemicals like insulin
and growth hormone which are made by protein
synthesis
It is possible to incorporate “foreign” DNA into
other organisms ---this is called transgenic or
transgenesis---dolly the sheep!
this is done so that an animal may be able to
produce something we need via their milk etc, or
plants by producing a natural insecticide to protect
themselves
vaccine production

To introduce the gene to the organism you
want to take up the new gene, and therefore
altered function, i.e. make a wheat plant be
resistant to insects after removing a gene you
know does this from say a nettle plant etc you
need to :

May use a gene which has been developed using the
bacteria plasmid and in terms of plants – a special
bacteria called AGROBACTERIUM is used which
infects the plant and acts as a natural genetic
engineer making the plant take on the new gene see
page 46


In animals there are three steps:
 Isolate the gene-using the restriction enzymes
 Inject the recombinant DNA with a fine glass
needle into the pro-nuclei in an embryo of that
organism 12-14 hours after fertilization
 Transfer the embryo to a recipient mother where it
can grow taking up that gene into all its cells as in
normal division
These are the transgenic organisms diagram
page 47


READ PAGE 48 OF Essentials and chapter 6?






M17.1 Understand that segments of DNA can be
multiplied and then have their base sequence
identified.
Humans can sequence even small amounts of
DNA:
1960-Fred Sanger
heated DNA so it separated
added DNA polymerase and excess of the base
nucleotides A,C,G, and T
Normally the primers would stick to the single
strands and polymerase would join the free
nucleotides with the corresponding bases until the
double helix was finished



Using four different test tubes he was able to see
when the sequence was stopped by identifying
which was the last nucleotide added before it
couldn’t add his altered A or T etc.. this meant he
could determine the sequence of DNA
DNA can be copied and amplified or copied lots to
the point where there is lots to analyse
This means you need to know the start of the
sequence of DNA you want to copy eg ATG and
use a primer which is a short piece of DNA that
matches this section you want to copy- i.e. TAC,
the primer joins to one strand of the DNA and
prevents it re-joining as a double helix


special DNA polymerase enzymes from
bacteria that don’t denature with heat along
with lots of copies of the primers and free
nucleotides are put in with DNA to increase
the chance of the primer finishing the strand of
DNA and not allowing it to re-join into its
original double helix; but to produce two
copies of the double helix
repeated heating and cooling (as long as there
is lots of primer and free nucleotides) lets us
make lots of copies of the DNA
THE POLYMERASE CHAIN REACTION –read
page 50
 EXPLORE DNA fingerprinting page 51 17.2
