3. LET’S START WITH THE BASIC……
PARASITE:
Etymologically parasite is derived from a latin
word parasitus, which means “person who eats at the table of
another”.
TYPICALLY DEFINED AS:
A living organism which lives and feeds on or/ in an organism of a
different species (host)and benefits by deriving nutrients at the other's
expense .The relation between them may be negative ,positive or
neutral .They may be ecto or endoparsites depending upon their area
of residence.
EX: ectoparasites= fleas or ticks
4. GENETIC CONTROL:
Any act of controlling any
condition or consequence by gene
expression at transcriptional or
translational level may be termed
as genetic control ..
Transcriptional control works by
controlling the number of RNA
transcripts of a region of DNA,
indirectly controlling protein
synthesis(translation)…
5. GENETIC CONTROL OF PARASITE…
The target population is not really replaced; rather a genetic
element is introduced into it, through breeding of released modified
mosquitoes with wild individuals, there by changing the phenotype of some or
all individuals in that population – those that carry the new genetic element.
The most familiar genetics-based population suppression strategy is
The Sterile Insect Technique (SIT) .
This technique relies on the release of large numbers of sterile
males to seek, court, and mate wild females, there by reducing the
reproductive potential of the target wild population. If enough of the wild
females mate sterile males then the target population will decline and
collapse.
6. The Sterile Insect Technique (SIT)
It is a type of birth control technique, which is species-specific
genetic “birth control”in which millions of males are sterilized(sterilized
by exposure to ionizing radiation using Cobalt60 or Cesium137
sources. Both isotopes emit gamma rays that cause breakages in the
chromosomes of the germ cells)with radiation & released them into
target area’s with regular intervals .
The sterile males then mate with native females,result of which
unfertile eggs are produced where there is no larval development to
continue next generation .when sufficient male insect are released
each successive generation will have few native insects & pollulation
will be suppressed & finally collapse.
EX: implemented in controlling of mosquito intermediate host
diseases like Malaria
dengue ,common fever, etc
7.
8. Other methods :
RIDL (Release of Insects carrying a Dominant Lethal)
The RIDL (Release of Insects Carrying a Dominant Lethal Gene) system proposed
by Thomas et al. (2000) consists of introducing a lethal dominant gene that could be
under control of a female-specific promoter, such as that of vitellogenin gene.
Expression of the lethal gene could be inactivated by treatment with tetracycline,
allowing a colony to be maintained. When male and female separation is required,
tetracycline is removed from the system, causing the death of all females. The RIDL
system is centered on the expression of tTA, a fusion protein that combines
sequence-specific tetracycline-repressible binding to tRe, a tetracycline-response
element, to a eukaryotic transcriptional activator. In the absence of tetracycline, this
protein will bind to the tRe sequence, activating transcription from a nearby minimal
promote .When preparing mosquitoes for release, the repressor is inactivated and
the lethal gene is expressed, causing the death of all females. When mating with
wild females, males homozygous for the lethal gene will produce heterozygous
progenies, of which only males will survive. Releasing of Insects carrying a
Dominant Lethal gene
9.
10.
11.
12. A sequence-specific nucleases called
homing endonucleases (HEGs) these are
the rare-cutting enzymes encoded by inteins
and introns. They are found inserted within
host genes. They catalyze the hydrolysis of
genomic DNA within the cells that synthesize
them.
