Lecture 1: Experimental Models Flashcards
Why can we use cells that are not human to study how human cells work?
- Humans consist of 5-10 trillion cells all having approximately the same DNA
- Every other animal, plant, or tiny critter is made up roughly of the same DNA/ proteins/ bacteria/ cell types
What makes a good experimental model?
- Is the organism used easy to rear?
- Is its rearing size convenient?
- Is it inexpensive to operate?
- Does the organism used have a short life cycle?
- Does the organism have a sequenced genome?
With so many experimental models available, how do scientists choose which model to
use?
- Cells have the same overall components (all originated from the same first cell)
- But some are more complex than others
- The model you choose is based on the question you are asking
What is micro size?
Cells
What is nano size?
Proteins
Why is it important to study cell biology?
Atoms = Matter = Cells = life
How many cell types are there
There are over 200 cell types
How many bacterial cells are colonizing humans
There are 50-100 trillion bacterial cells colonizing humans
E. Coli Model
- Bacteria
- Gave us an understanding of how DNA replication, gene expression and protein synthesis work
- Easy to keep
- Short life cycle (can divide every 20 mins)
- Simpler genome (4.6 million vs 3 billion)
Yeasts Model
- Simplest eukaryotes
- Shared characteristics with E.coli
- Easy to keep
- short life cycle (can divide every 2 hrs)
- Larger genome than E.coli, but simpler than humans
- Shared characteristics with humans
- Distinct nucleus
- Genomic DNA organized in 16 linear chromosomes
- Contains organelle
Prokaryotes vs. Eukaryotes
Prokaryotes
1. They are unicellular.
2. Cell wall is generally present.
3. Nucleus is absent, instead, they possess a nucleoid region in the cell.
4. DNA is Circular.
Eukaryotes
1. Could be either unicellular or multi-cellular.
2. Cell wall can be present or absent.
3. Nucleus is always present.
4. DNA is linear.
C.elegans Model
- Nematode (eukaryotic and multicellular)
- Small number of genes and cells (have been mapped out!)
- Good to study animal development and cell differentiation
- Can use mutations to study developmental abnormalities
- Similar genes have been found in humans
Drosophila Melanogaster Model
- Fruit fly
- Genome is larger than in C.elegans
- Easy to maintain
- Short reproductive cycle (~ 2 weeks)
- Good to study the molecular mechanisms of development
- As with C.elegans, similar genes and mechanisms exist in humans
Arabidopsis Thaliana Model
- Simple plant
- Small genome
- Easy to grow and maintain
- Methods for molecular genetic
manipulations are available - Identification of genes involved in plant development
Vertebrates ( Zebrafish)
- Easy to maintain
- Reproduce rapidly (3-4 months)
- Embryos develop outside the mother and are transparent
- Several molecular techniques available to map mutations
Vertebrates (Mouse (Mammal))
- More complex than other models
- Many mutations identified
- Several mutant mice available
- More applicable to medicine
- Similar genomes
- Mutations in homologous genes result in similar phenotypes
Cell Culture Model
- Allows for controlled manipulations
- Makes it easier to study signaling
mechanisms - Primary cultures vs. immortal cell lines
Cell Culture - HeLa cell line (Henrietta Lacks)
- First human cell line
- Derived from a cervical cancer
tumor in 1951(without consent
or knowledge) - A lot of people went on to benefit
financially (not her or her family
members) - Important for the development of
the polio vaccine
Viruses Model
- Intracellular parasites that cannot replicate on their own
- Smaller and simpler genomes
- Can be studied in cultured cells
- Discovered that some cancers
are caused by viruses
