OCR F215 Genomes and Gene Technologies

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F215 Module 2: Biotechnology and Gene Technologies
5.2.3 Genomes and Gene Technologies
(a) outline the steps involved in sequencing the genome of an organism
Genome ­ all the genetic information within an organism OR all the genetic information within an individual.
Genome sequencing ­ the technique used to give the base sequence of DNA of a particular organism.
1. Genomes are mapped to identify which part of the genome they have come from.
2. Samples of the genome are sheared (mechanically broken) into smaller sections of around 100,000 base pairs.
3. These sections are placed into separate bacterial artificial chromosomes (BACs) and transferred to E.coli cells.
As these cells grow in culture, many clones of the sections are produced ­ clone libraries.
4. PCR : DNA is extracted from BACs and replicated . Different restriction enzymes are used to cut the DNA into
smaller overlapping fragments.
5. Electrophoresis : The fragments are separated into size order. Computer programmes are used to reassemble
the full BAC sequence by analysing the overlaps shown by the fragment sequences.
Automated DNA Sequencing Based on Interrupted PCR and Electrophoresis:
Sequencing DNA fragments was initially slow using radioactively labelled nucleotides. The development of
automated sequencing has led to a rapid increase in the number of organism genomes sequenced and published
in recent years.
1. The primer joins (anneals) at the 5' end, allowing DNA polymerase to attach.
2. DNA polymerase adds free nucleotides by complementary base pairing the strand extends (PCR).
3. If a modified nucleotide is added, the DNA polymerase enzyme is `thrown off' and replication stops at that
point. The nucleotide is modified by adding different coloured fluorescent markers to different bases.
4. This process is repeated and many different sized DNA strands are created due to the random joining of
modified nucleotides. Some may only have one additional nucleotide added to the primer, others may have
5. The different sized DNA strands run through the machine ( electrophoresis ) sorting them from smallest length
first to the longest length. A laser reads the colour sequence of the modified nucleotide on the end of each
DNA strand, displaying the sequence of bases formed. Complementary base pairing of this sequence will tell
you the base sequence on the original DNA strand.
(b) outline how gene sequencing allows for genomewide comparisons between individuals and between
Genomics ­ the study of the whole set of genetic information in the form of the DNA base sequences that occur
in the cells of organisms of a particular species.
Comparative gene mapping ­ knowing the sequence of bases in a gene of one organism and being able to
compare genes for the same (or similar) proteins across a range of organisms.
The DNA of all organisms contains sections known as genes which code for the production of polypeptides and
proteins . However, this coding DNA is only 1.5% of the genome of humans. Much DNA is noncoding DNA and
has been referred to as junk DNA , which is misleading as this noncoding DNA carries out a number of regulatory
functions. Genomics is seeking to map the whole genome of an increasing number of organisms. Comparing genes

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F215 Module 2: Biotechnology and Gene Technologies
and regulatory sequences of different organisms will help us to understand the role of genetic information in a
range of areas including health, behaviour and evolutionary relationships between organisms.
Comparative gene mapping has a wide range of applications:
The identification of genes for proteins found in all/many living organisms shows the importance of these in
Comparing DNA/genes of different species shows evolutionary relationships .…read more

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F215 Module 2: Biotechnology and Gene Technologies
The DNA polymerase enzyme is described as ` thermophilic' because it is not denatured by the extreme
temperatures used in the process. The enzyme is derived from a thermophilic bacterium , Thermus aquaticus
( Taq ), which grows in hot springs at a temperature of 90o
C.…read more

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F215 Module 2: Biotechnology and Gene Technologies
Rstrain and heattreated Sstrain of pneumococcus = mouse dies .
The Rstrain was capable of taking up DNA from their surroundings (DNA from Sstrain), so synthesis of the
toxic protein occurred and killed the mouse.
(l) describe the advantages to microorganisms of the capacity to take up plasmid DNA from the
The advantage to the bacteria of conjugation is that it may contribute to genetic variation.…read more

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F215 Module 2: Biotechnology and Gene Technologies
6. The plasmids are mixed with bacteria, some of which take up the recombinant plasmids .
7. The bacteria are grown on agar plates, where each bacterial cell grows to produce a colony .
(o) outline the process involved in the genetic engineering of `Golden RiceTM '
Golden Riceis a type of genetically engineered rice produced to
reduce vitamin A deficiency . Vitamin A ( retinol ) in the diet only comes
from animal sources .…read more

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F215 Module 2: Biotechnology and Gene Technologies
Able to transplant organs that you could only Medical concerns about possible disease transfer
obtain from humans that are no longer alive, e.g. between the pig and the human.
heart. Some animal welfare groups strongly oppose
Pigs organs are roughly the same size ­ less likely killing animals in order to harvest organs for
to be rejected. human use.…read more

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F215 Module 2: Biotechnology and Gene Technologies
There are difficulties in getting the allele into the More straightforward, but considered unethical to
genome in a functioning state . Liposomes are used but engineer human embryos . It is not possible to know
these may be inefficient. whether the allele has been successfully introduced
Liposomes ­ small spheres of lipid bilayer containing without any unintentional changes to it, which may
a functioning allele . They can pass through the lipid damage the embryo .…read more


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