8.7 Problems with the synapses Flashcards
Dopamine
A neurotransmitter secreted by
neurones, including many of those located in
the midbrain. Parkinson’s disease involves the
death of some of these neurones and a reduction
in the amount of dopamine produced in the
brain. Knowledge of the structure and function
of dopamine has led to the development of
several successful approaches to relieving the
symptoms of Parkinson’s disease.
Agonist, Agonists
A substance which mimics the
action of a neurotransmitter at a synapse. The
molecules of an agonist have a similar shape to
the molecules of a particular neurotransmitter.
As a result they also fit into the receptor
molecules in the postsynaptic membrane of the
synapse. Neurotransmitters only exert their
effects for a short time because they are rapidly
broken down. Agonists on the other hand are not
broken down so readily and can continue to
stimulate the postsynaptic nerve cell. Agonists that mimic the neurotransmitter dopamine are
useful in the treatment of Parkinson’s disease.
Serotonin
A neurotransmitter released by
neurones situated in the brain stem which
targets a large area of the brain. Depression is
linked to a lack of serotonin and drugs used to
treat depression make use of this. They either
block the absorption of serotonin from the
synapse back into the presynaptic neurone or
they inhibit the action of enzymes which break
down serotonin.
Multifactorial
A condition, e.g. human height, in
which several genes and one or more
environmental factors are involved. Many
diseases are also multifactorial.
Ecstasy, MDMA
Ecstasy is an illegal
recreational drug. It contains the chemical
MDMA that affects thinking, mood and memory
in both the short and long term.
Human Genome Project
An international
research project to determine the base sequence
of the human genome, and those of other
organisms used in biological research such as
mice and rats. The first draft of the human
genome sequence was published in the journal
Nature in 2001.
Genome
All the DNA inside a cell. The genome
contains a full set of all the genes controlling the
growth and development of the organism of
which the cell is a part.
Single-nucleotide polymorphism, SNP
There is
a lot of DNA in a single human cell. DNA is
made up of a large number of nucleotides joined
to each other. Slight differences in the sequence
of these nucleotides result in individuals
differing from each other. A single-nucleotide
polymorphism or SNP is a variation in a single
nucleotide. Scientists have identified over a
million places where single-nucleotide
polymorphisms appear in humans.
Genetic modification/engineering
The process
by which organisms have new genes inserted
into them. For example, bacteria have been
genetically modified to contain a gene that can
make human insulin. An example of a
genetically modified plant is maize which
contains a bacterial gene. This enables the plant
to make an insecticide that kills caterpillars
feeding on the maize.
Transgenic
A transgenic organism is one which
has been genetically modified, i.e. one in which
new genes have been inserted. Maize plants
have been genetically modified to contain a
bacterial gene. This gene enables the plant to
make a substance which kills caterpillars that
feed on it and would otherwise destroy it. These
maize plants are described as transgenic because
they contain a gene from another organism.
Plasmid
A small, circular piece of DNA found in
the cells of many bacteria. Plasmids can be
transferred from one cell to another. They are
very useful in genetic engineering because they
can be used to insert new genes into the cells of
bacteria and plants.
Artificial selection
The process of humans
choosing plants or animals with desirable
characteristics to breed and increase the chance
that the offspring will have these characteristics.
Also known as selective breeding. Most
agricultural crops and domesticated animals are
the result of artificial selection. The allele
frequency in the population changes so evolution
of the species has taken place.
Marker gene
When organisms are genetically
modified, new genes are introduced into their
cells. To label cells that contain a new gene, a
marker gene is also inserted. The marker gene
may produce resistance to an antibiotic.
Incubating the cells with the antibiotic kills cells
which have not taken up the resistance gene
along with the other new gene. The use of
marker genes is an effective way of finding
those cells that have taken up the new gene.
Micropropagation
The production of new plants
from individual cells or small pieces of tissue.
By using this technique large numbers of
genetically modified plants can be produced
very rapidly from a single cell or callus. All the
tiny plantlets formed will be genetically
identical.
