Transcript 2012 Model Organism Good Versionx

PITT GENE TEAM:
MODEL ORGANISMS
MODULE
WHAT ARE MODEL
ORGANISMS AND
WHY DO SCIENTISTS
USE THEM?
DEFINITION OF MODEL
ORGANISMS
A model organism is a species that is extensively studied to understand
particular biological phenomena, with the expectation that discoveries made in
the organism model will provide insight into the workings of other organisms.
• In particular, model organisms are widely used to explore potential causes and
treatments for human disease when experimentation on humans would be
unfeasible or unethical.
•
MODEL ORGANISMS
Relatively cheap
• Can be easily grown
• Replicate quickly
• Small
• Various similarities to humans
•
SHORT MOLECULAR BIOLOGY OVERVIEW
Unity of Life
12 million
base pairs of
DNA
99 million
base pairs of
DNA
165 million
base pairs of
DNA
3 billion
base pairs of
DNA
3 billion base
pairs of DNA
6,000 genes,
of which at
least 31%
have human
equivalents
19,000
genes, of
which at least
40% have
human
equivalents
13,000
genes, of
which at least
50% have
human
equivalents
Almost every
human gene
has a
counterpart
in the mouse
~25,000
genes
E. COLI
Escherichia coli

Prokaryotic

Very simple cells


“Workhorse” for biological research


Used to work out the basics of fundamental cell processes like DNA
replication, transcription, and translation.
Used to make proteins and DNA molecules from other species that
scientists can then use for experimental tests
Medical applications


Used to manufacture human insulin for diabetics
Antibiotics
Yeast
Saccharomyces cerevisiae
(Budding yeast/Baker’s yeast)

Eukaryotic
 Can
be used to study basic cell processes like
transcription and translation, but also:
 Formation
of organelles
 Mitosis (nuclear division)

Was used to work out
control of the “cell cycle”
 Very
important for
understanding how cancer
develops
C. elegans
Caenorhabditis elegans (Worm)



Transparent
C. elegans can be used to
study muscle degradation
Also used to study apoptosis
(programmed cell death)
 During
the development of a
worm 1,090 cells are
generated but an adult
worm only contains 959 cells
Drospophila melanogaster
Drosophila melanogaster (Fruit fly)

Flies are used to
understand the
patterning of body
segments during
development.
Arabidopsis thaliana (mouse ear cress)

Useful in the study of:
 Photosynthesis
 Pest
resistance
 Disease resistance
 Small
5
genome
chromosomes
 Diploid

Researchers have
engineered Arabidopsis
plants that can sense
explosives or toxins in the
air and change color in
response
Mus musculus (mouse)



Mice are very similar
physiologically to humans
Many human illnesses occur or can
be induced in mice
Studies of the obese mouse have
yielded important information
about fat storage and metabolism.
Choice of model organism


The model organism that a scientist uses depends on
the question being investigated
Which model organism would you use to study:
 Root
formation?
 Hearing?
 Sexual reproduction?
 Metabolism?
 Infection?