Download Describe asexual reproduction What is

12/10/2015
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Describe asexual
reproduction
Involves only one
organism
Individuals produced
are genetically
identical i.e. clones
Give examples of natural and
artificial cloning
Natural: bacteria;
plants from suckers,
blubs, corms
Brought about in
plants by cell culture
What is
micropropagation
Cloning plants
Growth of a plant from
part of a plant or a few
cells in suitable growth
media
Describe the steps involved in
plant tissue culture
Explants placed in sterile, aerated
medium
Cells divide by mitosis to form
callus; callus is subdivided
Each piece differentiates into a
plantlet
Plantlets transplanted into sterile
soil when grown to suitable size
Define clone
A group of genetically identical organisms
formed from a single parent as a result of
asexual reproduction or by artificial means
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Define in vitro
fertilisation
What does embryo cloning in
animals involve
A technique which involves mixing the egg or
oocyte with sperm in a dish where
fertilisation takes place
IVF in a petri dish of the best
sperm and eggs
Splitting of an embryo before cell
division
And the subsequent growth of
cells into many individual embryos
What is meant by the
term stem cell
An undifferentiated cell capable of dividing to
give rise to cells which can develop into
different types of specialised cells
Describe cloning by
nuclear transfer
• Cells taken from tissues of udder of donor
sheep; cultured in medium that prevents
division
• Unfertilised egg removed from recipient
sheep and nucleus is removed
• Donor and recipient cells fused together by
a gentle electric pulse, allowed to divide to 8cell stage - ball of cells
• Developing embryo implanted into the
uterus of another sheep - surrogate; lamb
born identical to donor sheep
Describe the
advantages of
cloning
Speed of production, production of
large quantities, identical genetic
line of organisms
Enables desirable qualities to be
preserved for the next generation
(by conventional reproduction
beneficial mutation would be lost
due to reshuffling)
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Describe the
disadvantages of
cloning
Describe how cloning is used
to conserve rare breeds
In mammals, very expensive and
unreliable
Inadvertent selection of
disadvantageous alleles
Offspring may show long-term or
unforseen effects e.g. premature
ageing
In plants - disease/entry of
pathogens may cause problems
Embryos of young animals are bisected and
successfully transplanted into a surrogate
mother of a common breed to produce a new
individual of a rare type
Describe what tissue
engineering involves? What
are its applications
Inducing living cells to grow on a
framework of synthetic material to
produce a tissue e.g. skin
Treatment of extensive deep
burns; blood vessel replacement,
bone and cartilage repair and
treatment of degenerative nerve
diseases
What are the implications of
cloned stem cells in terms of
organ transplantation
Prevent immune
rejection
Reduce problem of
organ shortages
Describe the technique to
produce a cloned organ
Mature cell taken fro patient and
nucleus removed
Nucleus removed from human
ovum; mature cell nucleus
transferred into empty ovum
Ovum divides into a ball of stem
cells
Stem cells isolated and cultured
with appropriate growth factors
allowing their growth into the
desired organ
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Outline the ethics concerning
the use of stem cells
• Come from surplus embryos not placed in
uterus; embryos destroyed once stem cells
removed; some consider this unacceptable
even though embryos wouldn't develop
anyways
• Health benefits inc parkin, alz, heart, liver
outweigh
• Other sources of stem cells e.g. bone
marrow have more restricted medical
applications
• Slippery slope to reproductive cloning,
devalue human life - illegal in UK
Define totipotent
Cell which can differentiate
into a body cell
Define meristem
Growing points where cells
divide rapidly by mitosis
Why can micropropagation be
used as a cloning technique
Name some conventional
methods of plan propagation
Many plant
tissues are
totipotent
Grafting
Taking cuttings
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Which tissues in plants aren't
totipotent
Xylem and pholoem
Describe some advantages of
micropropagation
• Large numbers of plants grown in
controlled conditions ensuring greater
survival rate
•Less time consuming as pollination, seed
production, seasonal constraints aren't
required
•Good quality stock selected - e.g. disease
resistance
•Crop uniform - commercial
•Large plant/area ratio - heating and lighting
•Genotypes preserved; reduced space for
transport
Describe some applications of
cell cultures for medical and
research purposes
The culture of viruses for vaccine
production
Production of monoclonal
antibodies
Cell replacement therapy, tissue
engineering
Describe some disadvantages
of micropropagation
Sterile conditions must be
maintained
Plants genetically unstable increased mutation rate; regular
inspection required to remove
defects
Describe the aims of the
Human Genome Project
Identify all genes in human DNA
Determine sequences of 3 billion
bp
Store info in databases
Improve tools for data analysis
Transfer related technologies to
private sector
Address ethical, legal, social
issues that may arise
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What is meant by the
human genome?
All the DNA sequences
contained in the
chromosomes of an organism
What is meant by the
term gene probe?
Short piece of DNA, whose
sequence is complementary
to mutated sequences
What are the implications of
the Human Genome Project
in terms of inherited disease
Find exact base sequence
changes that cause the
disease
Describe how genetic
screening is carried out
DNA obtained from patient and
scanned for mutated sequences
Gene probes used to seek their
complement among the 3 billion
base pairs of individual's genome
Mutated sequence present =
binding and resultant flagging of
mutation
Describe another method of
DNA testing other than gene
screening
Patient's DNA
sequence of gene is
compared with normal
gene
Expensive
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Outline the main uses of
genetic testing
Describe the use of genetic
testing in terms of cystic
fibrosis
• Carrier screening (recessive)
•Pre-implantation diagnostic testing
•New-born baby screening
•Pre-symptomatic testing for predicting adultonset disorders - Huntington's
•Pre-symptomatic testing for estimating risk
of developing adult-cancers + alz
•Confirmation individual has disease
•Forensic/identity testing
Determine whether
person is carrying
faulty gene
Carrier parents may
decide not to have
children
Describe the use of genetic
screening in terms of cancers
and alzheimers
Determines likelihood of
developing diseases during
adulthood
Health authorities can target early
diagnosis, advice on reducing
risks
Describe the
advantages of gene
testing
Improves lives:
diagnosis + treatment;
children with diseases;
identify high risk
Describe some problems
concerning commercialised
gene tests
Targeted at pre-symptomatic
people with high risk
Difficulty interpreting positive
result because may be
interactions between several
genes/environment
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Describe some limitations of
gene testing
What is meant by
gene therapy?
Lab errors misidentification/contamination
Uncertainties in interpretation risk of stigmatisation, anxiety,
discrimination etc
Social concerns: who has access
to genetic info, how is used? Who
owns/controls info; should parents
have right to test children for
adult-onset diseases; Danger of
one day producing human clones
A technique whereby a defective gene is
replaced with a gene cloned from a healthy
individual to provide a potential cure for a
genetic disorder
What is the main obstacle
concerning gene therapy?
Developing gene delivery system
Inserting normal versions of gene
into person's cells
Ensuring their correct function
What are the two ways of
replacing defective genes
Gene therapy involving somatic
cells - therapeutic but not inherited
Germ-line therapy - introduction of
corrective genes into germ-line
cells
What is meant by the
term liposome?
Minute spheres of lipid
molecules, capable of
carrying DNA inside them
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Describes the problems that
arise due to cystic fibrosis
Produce thick, sticky mucus from
epithelial cells lining certain
passageways in body
Pancreatic duct becomes blocked
preventing enzymes reaching
duodenum
Bronchioles and alveoli of lungs
become clogged, causing
congestion and difficulty
breathing. Mucus difficult to
remove - recurrent infections
Describe why cystic fibrosis
occurs, with reference to its
deficient gene
Cystic fibrosis trans-membrane
regulator (CFTR) transports Clions out of cels into mucus
Sodium ions flow out of cells, and
water passes out by osmosis
So mucus is of a watery
consistency
Mutation means protein is one aa
different thus cannot perform
funtion
Describe the use of liposomes
in treating cystic fibrosis
Gene therapy
Genes inserted into liposomes can pass through lung epithelial
cells
Aerosol inhaler delivers the
liposomes
Liposome and cell surface
membrane fuse, DNA released
inside cell
Gene expressed
Describe the use of viruses in
treating cystic fibrosis
Virus rendered harmless
Virus cultured in epithelial cells
along with plasmids with normal
CFTR gene
Gene incorporated in viral DNA
Virus isolated and introduced to
patient by inhaler
Virus injects DNA which includes
normal CFTR gene into epithelial
cells of lung
For what can the current gene
therapy treatments for cystic
fibrosis not fix?
Cannot solve
digestive problems
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Describe the
formation of a
liposome
How effective is gene
therapy?
How is cystic fibrosis treated
on a day-to-day basis?
Plasmid DNA containing
theraputic gene incubated with
empty liposomes
-ve DNA binds with +ve liposomes
and plasmids absorbed
Liposomes containing plasmid
DNA are called lipoplexes
Short lived - usually repeated in
30-day intervals
May be immune response in
patient
But advantages outweigh the
caveats
Frequent daily chest
physiotherapy massage to
keep airways open
What is meant by
genetic counselling?
Advice for people with a family
history of a genetic disease - for
whether to have a child
Closely linked with genetic
screening - informs advice
Advice based on: history of
disorder in family; whether parents
closely related; frequency of faulty
gene in population
Allows parents to make personal
decisions
Describe different methods of
genetic screening
Blood tests - e.g. for CF
Amniocentesis - withdrawing
amniotic fluid during early stages
of preg. Cells that have floated
away from surface of embryo.
Analysed microscopically
Chorionic villus sampling - tiny
samples of foetal tissue withdrawn
from uterus and cells cultured and
examined under microscope
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Outline the advantages and
disadvantages of gene
therapy
D: invasion of privacy; increased
number of abortions; high risk
group for insurance purposes
(expensive/impossible to obtain);
decisions as to whether to have a
child; use of gene therapy for
wrong reasons - improving
appearance of child
What is meant by the
term clone
A population of genetically
identical cells or organisms
What is meant by the term
restriction enzyme?
Enzymes that cut DNA
molecules between specific
base sequences
What is meant by '
sticky ends'?
The two ends of the 'foreign' DNA segment.
They have a short row of unpaired bases
that match the complementary bases at the
two ends of the opened-up plasmid DNA
sample
Describe the uses of genetic
engineering
Genes into bacteria to make
useful products e.g. insulin
Genes into plants and animals to
acquire new characteristics e.g.
resistance to disease
Genes into humans so no longer
suffer disease like CF
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Outline the key steps in
genetic engineering
Isolation of DNA fragment
Insertion into vector
Transfer of DNA into suitable host
cells
Identification of host cells that
have taken up gene by use of
gene markers
Cloning of host cells
Describe how, in genetic
engineering, DNA is identified
and isolated Gene probe with complementary
sequence finds gene on DNA.
Restriction endonucleases cut
DNA into small pieces allowing
genes to be isolated - sticky ends
Or reverse transcriptase: mRNA
for gene extracted from cell;
enzyme added (from retroviruses)
makes copy DNA (cDNA) from
mRNA
DNA Polymerase added to
form dsDNA
What is EchoR1
What is the advantage of
using the reverse
transcriptase method?
What are the advantages of
using genetic engineering to
synthesise insulin?
Restriction enzyme
Palindrome
3'GAATTC5' and
5'CTTAAG3'
Cuts between Gs
forming sticky ends
Using mRNA carries specific
code for gene and not introns
found in DNA
Not used from animals
Large quantities
produced quickly and
p cheaply
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What is meant by the
term plasmid?
Circular loop of DNA found in
bacteria. Known as a vector
What is the function
of DNA ligase?
Ligation (sticking together) of
2 portions of DNA
What is meant by
recombinant DNA?
DNA which results from the
combination of DNA
fragments from two
organisms
Describe how a gene is
inserted into a vector in
genetic engineering
Why is the same restriction
enzyme used to cut donor
and vector DNA
Plasmids separated from cell
debris after bacterial cell wall is
dissolved
Rest. endo. used to cut plasmid
leaving sticky ends
Donor and vector DNA mixed
together - sticky ends bind; stuck
together by DNA ligases
Recomb. plasmid taken up by
treated bacteria, which multiply in
a fermenter
To ensure the sticky ends are
complementary
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Describe the transfer of DNA
into the host cell, including the
use of genetic markers
What is meant by the
term transgenic?
Plasmid used contains gene for
antibiotic resistance
Cells that take up recombinant
plasmid also take up this gene
Bacteria cultured in ampicillin;
only bacteria containing this
plasmid will survive (though some
plasmids may not contain the
gene
Gene replicated every time cell
divides
An organism that has had its genotype
altered producing a new strain of organism.
Also known as genetically modified
organisms
Describe how bacteria are
used to genetically modify
crops
Certain bacteria can cause plant
cells to multiply and form tumours
by inserting plasmid DNA into
genome of plant
Rest. enz. used to remove
tumour-forming gene, replacing it
with a gene for e.g. drug
resistance using methods outlined
before
Thus when recombinant bacteria
infect plant, gene for drug
resistance added to genome
Describe two
examples of GM
crops
Soya: major source of food;
treated to be tolerant to weed
killer; sprayed onto crops but only
weeds die; this breaks down in
soil into harmless component
Tomatoes: ripen when enzyme
breaks down pectin in cell wall;
complement of gene for enzyme
added to genome. Thus both
enzyme and complement
transcribed forming two mRNAs
which form a ds-mRNA molecule,
which cannot be translated - Flavr
Savr; longer shelf life of tomatoes
Describe the reasons why
some are opposed to GM
• Pollination - genes transfered to plants/wild
counterparts with unforeseen effects
• Some contain marker genes for antibio
resist - concerns of transfer back to bacteria
of intestine of consumer
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some are opposed to GM
crops
of intestine of consumer
• Commercialisation leads to decrease in
biodiversity of crops meaning susceptibility
to attack increases
• Commercial growth could comprimise
organic farming due to cross pollination by
wind and insects
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Describe the benefits of the
use of GM crops
What is meant by the term
electrophoresis?
What facet of human DNA
means genetic fingerprinting
can be carried out
Describe how genetic
fingerprinting is carried out
Describe the principal by
which gel electrophoresis is
governed
Improved food: flavour + keeping
qualities
Introduction of nitrogen-fixing
genes reducing dependence on
artificial fertilisers
Resistance to insects, weeds and
diseases
Resilience to disease in animals
esp in 3rd world
Exposing fragments of DNA
to an electric current in a gel
trough
Much of DNA has no known
function
Non-coding DNA sequences vary
in length - HVRs and STRs
The lengths of these regions
(alleles) are passed onto offspring
• DNA extracted and cut into small frags by
rest. endo.• Fragments separated by
electrophoresis• Southern blotting - trough
covered in nylon membrane and fragments
transferred• Radioactive DNA probes attach
to specific parts of the fragments and any
unbound fragments wash off• Membrane
placed under X-ray film and image develops•
Autoradiograph reveals pattern of light and
dark bands (dark = presence of radioactive
DNA) - unique
DNA is negatively charged so will
be repelled by negative charge
and attracted to positive charge
Larger DNA fragments will
encounter more resistance
(hydrogen bonds etc) so will move
more slowly
Thus in a given time a larger DNA
fragment will have moved less far
than a shorter DNA fragment
Hence DNA fragments can be
separated by length
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What are used in place of
radioactive probes in modern
genetic fingerprinting
How is a paternity
test carried out
Chemiluminescent
probes
Fingerprint of WBCs of mother
and father
Bands from mother subtracted
from child's patten
If father - must possess all
remaining bands
What is meant by the
term primer?
Short sequences of
nucleotides
What is in the reaction
mixture for PCR?
Sample of DNA
Buffer
DNA polymerase
Nucleotides
Primers
What is the function
of primers in PCR?
Act as signals to the DNA
polymerase to start copying
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Describe the process
of PCR
Why to forensic scientists
often use PCR when
producing a genetic
fingerprint?
Target DNA heated to 95ºC - 2
single strands
Solution cooled to 55ºC triggering
primers to joint to complementary
base sequences on each of the
single strands of DNA. This
triggers DNA replication
Solution heated to 70ºC and DNA
polymerase catalyses synthesis of
complementary strand for each of
the single strands of DNA; Repeat
Increasing the quantity of
DNA because the sample
obtained at crime scene may
be very small
Describe some issues of
privacy that arise in the study
of genetics
Who has access to
data
Insurance companies
Describe some advantages of
genetic engineering
Large-scale production of complex
proteins and peptides that cannot
be made by other methods
Production of higher yielding
crops, drug. res. keeping etc
Health benefits for treating genetic
diseases
Outline some concerns with
genetic engineering Germ-line therapy - insufficient
knowledge on the interaction
between genes - unforeseen
effects in future generations
Impossible to predict
consequences of genetically
engineered animals/plants
released into environment
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Describe the potential
hazards of genetic
engineering
Change in gene function microorganism into pathogen
Bacteria may result in
incorporation of recombinant DNA
into other species e.g. herbicides
into weeds
Transfer of antibiotic resistance
genes into pathogens
Tampering with oncogenes,
triggering cancer
Describe some problems
associated with recombinant
DNA technology
• Technically complicated - expensive on
industrial scale
• Identifying genes of value on huge genome
• Synthesis of required protein may require
several genes to code for several
polypeptides
• Treatment of human DNA with rest. enz.
produces millions of fragments of no use
• Not all eukaryotic genes can express
themselves in prokaryotic cells
What are exons?
Regions of DNA that
code for proteins
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