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1
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In other words, it codes for the respressor of the Lac-operon
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 The promoter is the binding site for RNA polymerase, the enzyme that performs
transcription
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The
opera to overlaps with the promoter, and when the lac repressor is bound, RNA
polymerase cannot bind to the promoter and start transcription
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 The operator overlaps with the promoter, and when the lac repressor is bound, RNA
polymerase cannot bind to the promoter and start transcription
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Describe how DNA would be packaged in the nucleus of a eukaryotic cell
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DNA is a negatively
charged polymer, packed compactly within the chromatin engirdling the histone proteins, a
ball of positively charged proteins
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In order to fit
in the DNA molecules into the nucleus, it needs to be packed into an extremely compressed
and compact structure called chromatin
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The nucleosomes are further coiled which results in the formation of chromatin
fibres
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These chromatin fibres condense to form chromosomes during mitosis
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Histone
proteins are positively charged possessing several arginine and lysine amino acids binding to
the negatively charged DNA
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Two H3, H4 dimers and two H2A, H2B dimers
form an octamer
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Histones can be modified to change the amount of packaging a DNA does
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This results in tight DNA packaging
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Enzymes that add methyl groups to histones are called histone methyltransferases
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3
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This copy, called a
messenger RNA (mRNA) molecule, leaves the cell nucleus and enters the cytoplasm, where
it directs the synthesis of the protein, which it encodes
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Specifically, RNA
polymerase builds an RNA strand in the 5' to 3' direction, adding each new nucleotide to the
3' end of the strand
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Initiation
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Each gene (or group of co-transcribed genes, in bacteria) has its own promoter
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Elongation
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As it
"reads" this template one base at a time, the polymerase builds an RNA molecule out of
complementary nucleotides, making a chain that grows from 5' to 3'
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Termination
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Once they are
transcribed, they cause the transcript to be released from the RNA polymerase
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The diagram in Q1 shows the lac operon
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coli bacteria can break down lactose, but it's not their favorite fuel
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Glucose requires fewer steps and less energy to break down
than lactose
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coli will go right ahead
and use it as an energy source
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To be as efficient as possible, E
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Bound CAP helps RNA polymerase attach to
the lac operon promoter
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This allows RNA polymerase to move
forward on the DNA and transcribe the operon
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They lead to strong transcription of the lac operon and production of
enzymes needed for lactose utilization
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That's because
the lac repressor remains bound to the operator and prevents transcription by RNA
polymerase
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5
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During translation, an mRNA sequence is read
using the genetic code, which is a set of rules that defines how an mRNA sequence is to be
translated into the 20-letter code of amino acids, which are the building blocks of proteins
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Translation occurs in a structure
called the ribosome, which is a factory for the synthesis of proteins
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Translation of an mRNA molecule by the ribosome
occurs in three stages: initiation, elongation, and termination
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Then a transfer RNA (tRNA)
molecule carrying the amino acid methionine binds to what is called the start codon of the
mRNA sequence
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Next, the large ribosomal subunit binds to form the complete initiation
complex
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Each corresponding amino acid is added to the growing chain and linked via a bond called a
peptide bond
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Lastly, termination occurs
when the ribosome reaches a stop codon (UAA, UAG, and UGA)
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The new protein is then released, and the translation complex comes apart
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In camels, like in all other mammals, milk is produced by the mammary glands
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The structure of the casein gene is
shown on the diagram below
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Describe the sequence of
events that needed to go from casein pre-mRNA to casein protein
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In alternative splicing,
certain exons are either included or excluded, resulting in different splice products
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One important step in eukaryotic
gene regulation is splicing, the removal of intronic sequences from pre-messenger RNA
(mRNA) precursors to yield mature mRNAs
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In alternative splicing, certain exons are either included or
excluded (skipped) to yield distinct mRNA and potentially protein isoforms
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Alternative splicing is thought to be key to transcriptome and proteome
complexity in higher eukaryotes In camels casein gene introns will be removed by the
process of splicing and exons will be successfully transcribed into mature mRNA
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All the steps of the
molecular central dogma i
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7
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(2)

Post-translational modification (PTM) of proteins refers to the chemical changes that
occur after a protein has been produced
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Milk proteins exhibit conformational structure due to post translational modifications and
constitutive levels of proteolytic activity produce a range of significant peptides
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Casein phosphorylation at amino acid serine or threonine is
catalyzed by kinase enzymes
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Caseins
exhibit a high degree of heterogeneity as a result of post-translational modifications (PTMs)
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κ-Casein has
long been known to exhibit a high degree of variability in glycosylation
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What are the general features of a prokaryotic expression vector?

(3)

Caseins exhibit a high degree of heterogeneity as a result of post-translational modifications
(PTMs)
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κCasein has long been known to exhibit a high degree of variability in glycosylation
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The vector is used to introduce a specific gene into a
target cell, and can commandeer the cell's mechanism for protein synthesis to produce the
protein encoded by the gene
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The vector is engineered to contain regulatory sequences that act as enhancer and promoter
regions and lead to efficient transcription of the gene carried on the expression vector
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The expression of a protein may be tightly controlled, and the
protein is only produced in significant quantity when necessary through the use of an inducer,
in some systems however the protein may be expressed constitutively
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An
example of the use of expression vector is the production of insulin, which is used for
medical treatments of diabetes
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The cloned gene may be transferred from a specialized
cloning vector to an expression vector, although it is possible to clone directly into an
expression vector
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Vectors
used for protein production in organisms other than E
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coli, elements that allow them to be maintained
in another organism, and these vectors are called shuttle vectors
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What is the name of the technique employed to encourage the uptake of plasmids by
bacteria cells?
(1)

The bacteria are given a heat shock, which causes some of them to take up a plasmid
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It appears that the heat shock causes the formation of pores in
the bacterial membrane, through which the DNA molecules can pass
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Spider silk can be produced in transgenic goats
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Explain why a mammary cell-specific promoter sequence is used in the
construction of the recombinant DNA
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The promoter sequence is isolated from the upstream region of the
mammalian endogenous gene
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Due to these reasons the memory cell specific
promoters are used in recombinant DNA construction

b
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11
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The Ti plasmid naturally inserts into the
genome of dicotyledonous plants
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Give a brief description of the method used to genetically modify plants using the Ti
plasmid
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Plasmid Ti is a soil-borne disease caused by Agrobacterium tumefaciens
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The Agrobacterium-mediated transformation process includes many steps:
 Isolate the target gene from the original organism
 Develop a functional transgenic construct containing the target gene; automatically
express the promoter; modify the codon if necessary to successfully increase the
protein Yield; and marker genes to facilitate the tracking of genes introduced into the
host plant
 Insert the transgene into the Ti plasmid
 Introduce the plasmid containing T-DNA into Agrobacterium
 Transfer the transformed Agrobacterium Mixing with plant cells to allow T-DNA
transfer to plant chromosomes
 Regenerating the transformed cells into transgenic (GM) plants
 Testing the characteristics or expression of the transgene in the laboratory, greenhouse
and field
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Describe the general features of a batch fermentation process

(2)

Batch fermentation is a so-called "closed system" in which substrates and producing
microorganisms are added to the system at zero time and are only removed after the
fermentation is over
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Bacteriocin production-Generally, its fed-batch fermentation technology has a
wide range of applications in production and research, including cell proteins, amino acids,
growth hormones, antibiotics, vitamins, enzymes, organic solvents, organic acids, nucleotides
and polymers
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Describe the general features of a continuous-flow fermentation process (2)
In continuous fermentation, fresh medium is continuously added to the fermentor, while the
used medium and cells are collected
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If the rate of addition and removal is the same, the volume of the
culture will remain constant
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Continuous cultivation is more efficient because the fermenter can be
operated continuously
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14
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(3)
A batch process refers to a process that includes a series of steps executed in a specific order,
while a continuous process refers to the flow of a product unit without interrupting time,
content, or expansion between each step of the process
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If you do not consider blocking, the process is in progress
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Human anti-thrombin DNA can be used to produce transgenic bacterial cells
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(2)
Goods are best choice due to short generation time and easily available
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16
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(4)

There are many methods for protein purification one of the method is Extraction
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There are multiple ways to do this
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The choice of method depends on the fragility of the protein and the
resistance of the cell
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by centrifugation
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If the
protein is sensitive to proteolysis, it is usually necessary to act quickly and keep the extract
cold
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17
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Include the organism used, the process
used to generate the end product and the use of the end product
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10 minutes before adding culture
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Finally, pasteurization can
effectively remove disease-causing bacteria
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Skimmed milk powder should also be added before heating to prevent
milk protein from coagulating
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The
ingredients are mixed uniformly to obtain a more stable consistency
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Longterm storage will thicken the yogurt
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At this stage, the warm mixture is inoculated with a live bacterial culture
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The bacteria used to make
yogurt are thermophilic, which is their optimal temperature range; they die at temperatures
above 130°F and do not grow much below 98°F
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6, the yogurt will
solidify
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Once the pH is reached, the yogurt is cooled to about 45°F to complete the
fermentation process
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Before fermentation
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Next,
pack the yogurt
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Total = 47
Pass = 28



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