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gene arrays (Kodama Y, Nakao Y, Nakamura
N, Fujimura T, Shirahige K and Ashikari T). The results confirm that there are
three types of chromosomes in lager brewing yeast: Sc-type, non-Sc-type, and
various chemical types.

            The
precise structures of the chimera-type chromosomes were determined by the links

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of forward-reverse shotgun read pairs.
The recombination break points between Sc-type and non-Sc-type chromosomes were
also confirmed by PCR using Sc-type and non-Sc-type sequences as primers and
subsequent sequencing of PCR fragments. “Polymerase chain reaction (PCR)

is a testing method that can be used to
assess the health and purity of yeast cultures” (” Polymerase Chain Reaction”).
These analyses showed that the lager brewing yeast contains at least eight
chimerical chromosomes. The chromosomes VIII, X, and XI, have a complicated
situation, as they appear even more complicated. They come in three types: pure
Sc-type, pure non-Sc-type, and chimerical ones. The report of competitive
genome hybridization using S. cerevisiae DNA with Cy3-, Cy5-labelled DNA (Bond
et al. 2004). Some of the chromosomal breakpoints were found to be inside ORFs,
which means that some hybrid ORFs exist. Most of these were classified as
“non-Sc” ORFs according to the relatively low nucleotide identities to S.
cerevisiae ORFs. It is to be anticipated that the further investigation of such
hybrid ORFs will be highly rewarding in terms of new knowledge on protein
function as well as hybrid speciation.

            Understanding
the genomic structure of one brewing yeast leads to the question: Do all lager
brewing yeasts have the same set up? In other words, to what exact extent are
these industrial organisms historically related? Some data on this matter are
becoming available from studies of comparative genomic hybridization between
genomic DNA of various lager brewing

yeast strains and various type strains,
with S. cerevisiae yeast DNA microarrays (Kodama Y, Nakao Y, Nakamura N,
Fujimura T, Shirahige K, and Ashikari T). Only Sc-type gene fragments hybridise
to the S. cerevisiae and therefore, the hybridisation signal reflects the
relative content of Sc-type DNA to non-Sc-type DNA.  Even though most of the tested lager brewing
yeast strains have the same structure, three show divergent structures. These
results raise interesting questions on the forces that control the evolution of
hybrid organisms. Further investigations in this field will certainly yield
information on the history of individual genes.

            With
that technological and scientific understanding of yeast, we can look into the past,
see the alternatives used, and see how beer making has changed throughout the
years. The fondness of humanity for consuming alcohol is common to all
civilizations and dates to the beginning of recorded history. Examples of
alcoholic drinks can be found on every continent. They have been consumed as a
part of a diet but because of the physiological effect of alcohol, they have
also often been associated with religious or ritual ceremony (Boulton et al). Beer
produced by primitive societies has been made from a source of sugar, usually a
cereal, to provide the alcohol. Likely, the early fermentations were
accidental. Therefore, wherever any natural source of sugar is to be
accompanied by yeast contamination, providing a supply of water, fermentation
would occur. It is known that the preparation of some native beers that used
cereals as a source involved a step where the grains where chewed by the
brewer. “The addition of saliva, which contains the amylase, ptyalin, would partially
degrade the starch content of the grain and thereby increase the fermentability
of the wort.” (Boulton et al) The effects of fermentation extend to the
quantity of bacteria of the product. In addition, the preparation of many beers
includes boiling, which alone would have a sterilizing effect. In historical
times, therefore, beer was a useful source of nutrients.

Origins of the
discovery of fermentation are lost. However, archeologists suggest that brewing
has been a community-involving activity for at least five thousand years. It is
reported that in ancient Mesopotamia forty percent of cereal crops were used
for brewing (Corran, 1975). The skills of malting cereals, to release
fermentable sugars from starch, were also discovered (Samuel & Bolt, 1995; Samuel,
1996). Corran (1975) speculates that it may have been because grains which had
been stored under wet conditions potentially give an increased yield of
alcohol. It is likely that such experience would have provided a stimulus for
further experimentation. However, the same author also suggests that primitive
malting may also have arisen as part of ordinary cooking. Cooking renders and
makes the grain more nutritious and digestible. The classical civilizations, such
as Greece and Rome, have no history of brewing, since they drank wine, probably
another skill acquired by accident.

The rise of modern
brewing started in Northern Europe. There is a possibility that some of the
skills came from the Middle East, although independent discovery may also have occurred.
By medieval times, brewing was an everyday thing.” In Burton-upon-Trent in the
United Kingdom, the abbey founded in the eleventh century had a brewery whose
product formed the reputation of this town as a center of brewing excellence.”
(Boulton et al). Belgian beers owe much to the skills of the medieval brewers.
A few of these breweries have survived and still produce, “the specialist
bottle-conditioned Trappist beers.” (Boulton et al)

Beer was popular which is reflected in
the fact that it was the staple drink of all classes. Sambrook (1996) says that
ale consumption in single medieval noble households were usually in the range
of seven hundred and fifty to fifteen hundred hectoliters. The widespread in
popularity of beer was probably heavily influenced by later Saxon and Danish
invasions (Hackwood, 1985).

The benefits of using
hops in brewing were known in ancient past and records exist detailing their
cultivation in ancient Babylon (Corran, 1975). This knowledge was passed to
Europe. Initially hops were used with other herbs such as rosemary, bog myrtle,
sweet gale, 

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