Plasmids

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16 Δεκ 2012 (πριν από 4 χρόνια και 6 μήνες)

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Control & Manipulation of Genes


Before Transcription


Access


Acetylation

loosens grip of histone, allowing access of
polymerase to DNA


Methylation

of an allele blocks that gene’s affect


How transcribed


Gene sequences rearranged or multiplied, generate
large amounts of gene product



Transcription Processing


mRNA cannot pass out of nucleus without
transport protein


Some proteins can block translation from starting


Translation Control


Affect ribosome components (no
rRNA
, no
translation)


Control speed of breaking down mRNA (how many
times it can be reused)



X Chromosome
Inactivation


Females XX


One X chromosome is
75% “shut down”


Barr body

condensed X
chromosome


Random


Operon

arrangement of promoter and
operators that control access to a gene


Lac

operon

in
E. coli
cells


E. coli
normally doesn’t use lactose (milk sugar)


Lac

operon

binds to gene that would allow use of
lactose, prevents it’s transcription


When glucose is scarce but lactose present,
activator is synthesized


Activator then prevents
lac

operon

from
functioning, allowing lactose to be used


Inhibition can be reversed


Recombinant DNA

any DNA molecule
consisting of base sequences from two or
more organisms of the same or different
species.


Able to combine genetic sequence of
different species


Restriction enzymes


Plasmids & cloning vectors


A
restriction enzyme

is added to a solution
with DNA


Enzyme “cuts” DNA at a specific place


Can fuse with DNA molecule “cut” with same
enzyme


Bacteria have two forms of DNA


One chromosome, a single circular DNA strand


Plasmids

small circles of “extra” DNA with only
a few genes


Bacteria divide rapidly, providing many new
organisms in a short period of time.



In nature, bacteria can share characteristics
through plasmids


Antibiotic resistance


With restriction
enzymes, can
splice DNA into
plasmid


Plasmid taken
into bacteria cells


“Donor” gene is
used by bacteria,
produces product
of gene


Is now part of
bacteria’s genetic
code, is passed on
during division


Uses


Laboratory studies of specific genes


Produce products quickly & cheaply


Insluin


Antibiotics


Vaccines


Animal diseases


HIV


Ebola


Polymerase Chain Reaction (PCR)

method to
reproduce fragments of DNA millions or
billions of time


Primer

short stretch of synthetic, single
-
stranded DNA


Primers are added to solution with DNA
fragments and polymerase


Solution is heated, denaturing and “opening”
DNA


Solution is cooled


Primers attach to matching base pairs during
cooling


Polymerase starts at primer, synthesizes DNA
chain


Process is repeated



Each “cycle” results in exponential growth


Quickly grow a segment of DNA


Uses


Forensics


Diagnostics (viral & bacterial diseases)


Paternity or relationship testing


Historical analysis


Mummies, mammoths, etc.


DNA is mixed with certain
compounds in a solution


The solution is placed into
a gelatinous substance


Electrical charge is
carried along the gel


The DNA separates along
the gel in a pattern based
on the structure and
weight of the individual
genes


Everyone’s DNA is unique
to them


Base
-
pair patterns
different between people


PCR & electrophoresis to
find & analyze DNA


1 in 3,000,000,000,000
chance of unrelated
people having identical
DNA


1988

National Institutes of Health
combined previously begun research
into one project


2003

Human genome officially
completed


Almost 20,000 confirmed genes


Over 2,000 possible genes


Don’t know what all of these genes
do!


Much of human genome DOESN’T
code for proteins


Many might regulate expression of
other genes…. “Master Control”
genes


Study diseases & disorders


Be able to predict and detect disease


Gene therapy

transfer one or more normal
or modified genes into a person’s body cells


Correct genetic defect


Boost resistance to disease


Imperfect at this time


Bacteria


Insulin


Blood
-
clotting factors


Hemoglobin


Vaccines


Environmental clean
-
up


Oil spills


Pollutants


Radioactive waste


Plants


Drought resistance


Disease resistance


Herbicide resistance


Soil tolerance


Greater yield


Better nutrition


Animals


Medical research


Mice susceptible to human
diseases


Disease resistance


Environmental resistance


Featherless chickens


Medical proteins



Cattle

human collagen
(cartilage, bone, skin repair)


Better nutrition


Low
-
fat pigs