E.coli inhabits the lower gastro-intestinal
tract of warm blooded animals, (survive in presence of bile salts)
and survive outside the body by spreading through the feces. Since
the bacteria canthrive in different conditions, it is an advantage
to use it as a model organism. The attributes that makeit fit as a
model organism are:
- It is single celled
- easy genetic manipulation
- rapid growth and reproduction to obtain generations within no
time
- survival in variable growth conditions
- E.coli poses less or no harm to the scientists
The limitations of using e.coli as a model organism is that they
are prokaryotic and humans are eukaryotes hence their(eukaryotic)
genome is more complex and larger.
Yeast is an eukaryotic unicellular organism,
hence there are a few similarities with humans whicharefar more
complex. The advantages of usin Yeast as a model organism
include:
- They have common biological properties as humans since they are
eukaryotic
- Genetic manipulation is easy and cheap compared to complex
organisms like mice and rat.
- They share a few genes with humans, socan be used to test new
drugs.
- Their cells are similar to human cells but grow rapidly
- Complete genome sequence is available and all genes are
studied
Limitations of using yeast as a model organism include:
- proteins which are found similar may have organism specific
functions hence they may not fuction in the same way in other
organisms of different species
- yeast has a fewer genes compared to humans
- yeasts have specific processess which are not found in other
organisms
Invertebrates:
Using C.elegans as a model organism has the following
advantages:
- These organisms have gut, neurons, tissues, skin that are
similar in function, form and genetics of humans.
- It can be grown cheaply
- C.elegans cultures can be frozen and revived when needed
- Short life cycle which helps in studying their development
- Many of the molecular signals controlling its development are
found in humans
- Many of its genes have functional counterparts in humans making
it useful model in human diseases
Limitations include:
- They have a simple body plan
- do not have defined tissues and organs like brain, blood and
internal organs
- They are evolutionarily distant from humans
Drosophila melanogaster's advantages as a model organism:
- Short life cycle with a generation time of 12 days
- It has a small size and produced in large numbers
- It has 60% genes involved in human genetic diseases
- it has only 8 chromosomes hence, used in genetic studies
- it has anatomical features making easy characterization
Limitations of drosophila:
- Anatomy of brain and other organs is different from humans
- Since they are invertebrates, there is a risk of ignoring
important pathogenic factors which are vertebrate specific
- Cannot accurately predict the effect of drugs in humans
- drug delivery is difficult
Using mice as a model organism has the following advantages:
- 99% of their genome is similar to that of humans
- Its small size facilitates large scale throughput studies
making it cost effective model
- They are easy to care, breed and study and can be well adapted
to new surroundings
- Since they have longer life spans of previously used models,
they can be used to study disorders of ageing, neurological
disorders, heart diseases, stress, high blood pressure,
obesity
- They are mild tempered and docile, making them to handle
easily
limitations of using mice as a model organism:
- research mice are inbred and donot undergo genetic variations
existing in humans
- They fail to mimic human disease phenotypes