1. FRUIT FLY AND ZEBRA FISH
AS MODEL ORGANISMS
P:4 U:2
VEDANTI GHARAT
M.SC. PART-1
ROLL NO. - 09
2. MODEL ORGANISM
• A model organism is a species that has been widely studied, usually
because it is easy to maintain and breed in a laboratory setting and
has particular experimental advantages.
• Model organisms are non-human species that are used in the laboratory
to help scientists understand biological processes.
• For example, they may have particularly robust embryos that are easily
studied and manipulated in the lab, this is useful for scientists studying
development.
• Or they may occupy a pivotal position in the evolutionary tree, this is
useful for scientists studying evolution.
3. WHY ARE MODEL ORGANISMS USEFUL IN
GENETICS RESEARCH?
• Many model organisms can breed in large numbers.
• Some have a very short generation time, so several generations can be
followed at once.
• Mutants allow scientists to study certain characteristics or diseases. These
are model organisms that have undergone a change or mutation in
their DNA that may result in a change in a certain characteristic.
• Some model organisms have similar genes or similar-sized genomes to
humans.
• Model organisms can be used to create highly detailed genetic maps:
• Genetic maps are a visual representation of the location of different genes on
a chromosome, a bit like a real map but one where the key landmarks are
areas of interest in the genome.
5. FRUIT FLY (DROSOPHILA MELANOGASTER)
• Drosophila melanogaster, commonly known as the fruit fly, remains one of the
most commonly used model organisms for biomedical science.
• There are many technical advantages of using Drosophila over vertebrate models;
1. they are easy and inexpensive to culture in laboratory conditions
2. have a much shorter life cycle
3. they produce large numbers of externally laid embryos
4. they can be genetically modified in numerous ways
5. Their genome is sequenced
• It has been used productively as a model organism for over a century to study a
diverse range of biological processes including genetics and inheritance,
embryonic development, learning, behavior, and aging.
6. • In 1995, scientists won the Nobel Prize in Physiology or Medicine “for their
discoveries concerning the genetic control of early embryonic development of
fruit fly”.
• One of the first mutations Morgan isolated is known as white; flies with this
mutation have white eyes (instead of red). So, various genetic defects are
available.
• Drosophila undergo a four stage life cycle; egg, larva, pupa, and fly.
• The regenerative capacity of Drosophila imaginal discs has been studied. The
cells in these discs do proliferate, but do not differentiate.
• Drosophila as a model for wound healing has been studied recently.
• Drosophila is emerging as a valuable system for use in the clinical drug
discovery process.
• New drugs can be tested in Drosophila much faster than in mammalian
models.
• Furthermore, when using Drosophila, it may be relatively easy to manipulate
the genetic background to mimic a diseased state to test for drug efficacy in
that context.
7.
8. ZEBRA FISH (DANIO RERIO)
• The zebrafish, Danio rerio, is a fast expanding and extremely valuable
model system for studying vertebrate developmental biology.
• Unlike mice, zebrafish embryos develop quickly and externally to their
mothers, and are transparent, making it easier to study the development of
internal structures and organs.
• Because of its fully sequenced genome, easy genetic manipulation, high
fecundity, external fertilization and rapid development, and nearly transparent
embryo, zebrafish are a unique model animal for biomedical research,
including studies of biological processes and human diseases.
• 70% of human genes have a counterpart in zebrafish.
• Zebrafish has all the main organs involved in the process of metabolism and
can be used to study several human metabolic disorders.
9.
10. • Targeted mutation has been demonstrated in zebrafish using zinc-finger nucleases,
TALENs, and more recently CRISPR/Cas9.
• Another popular targeted gene deactivation method in zebrafish are short, modified
oligonucleotides called morpholinos.
• Strategies for generating transgenic zebrafish are well established, One common and
robust strategy uses a transposon called Tol2 to randomly integrate foreign DNA into
the genome.
• Disadvantages include their duplicated (i.e., redundant) genome, their long three-
month generation time and labor-intensive maintenance compared to invertebrate
model systems, and their resistance to facile CRISPR/Cas9-mediated insertion of
foreign DNA.
