MODEL ORGANISM

Mouse (Mus musculus) or the Fruitfly (Drosophila melanogaster)

first generation organisms to be used as genetic models because of their characterized genetics and ease in experimentation

Human genome project (___)

voyage of biological discovery led by international group of researchers looking to comprehensively study all of the DNA of a select set of organisms

Bacteria ___
Yeast ___
Fruitfly ___
Roundworm ___
Mouse___

Five model organism

Danio rerio (zebra fish), Chick embryo, Arabidopsis thaliana (mustart plant)

aside from 5 model organism are…

BACTERIA

The foundations of molecular biology were based on studies of bacteria

Bacteria as model oroganism

• Antibiotics

• Recombinant DNA technologies

Theodor Escherich

the German microbiologist and pediatrician, began to study the infant gut microbes and its role in the digestion and disease.

Theodor Escherish

he discovered a fast-growing bacterium called ‘Bacterium coli commune’ – now known as Escherichia coli

‘Bacterium coli commune’

fast-growing bacterium

Escherichia coli

usually used for recombinant DNA technology, and used to associate specific disease of the genome of individual; this discovery led to invention of drugs and therapies; have been proven to be a useful model system in which to investigate protein structure and function

E. coli

is an excellent model organism for geneticist because of variety of reasons: small, take up very little lab space, easy to grow

E. coli

has short doubling time [15-20 mins] under ideal growth conditions

YEAST

• Eukaryotic system.

• Signaling molecules and cell cycle are nearly similar.

• Good model system to understand many human diseases including cancer

yeast

• Ease of genetic manipulation allows its use for analyzing and functionally dissecting gene products from other eukaryotes.

• Last decade four Nobel prizes were awarded for discoveries involving yeast.

Baker’s Yeast or Saccharomyces cerevisiae

is known to be among the best experimental organism

MSH2 = Muts Homolog 2 and MLH1 = Mut L Homolog 1

these genes are involved in hereditary non-polyposis colorectal cancer in humans and examining these genes help scientists to know more about the role of MSH2 and MLH1 in colon cancer

YEAST

organism which has MSH2 = Muts Homolog 2 and MLH1 = Mut L Homolog 1 similar to humans

Linkage

Term which refers ro the likelihood of two alleles to be inherited together

Plasmid

known to be the first vectors developed

Caenorhabditis elegans

roundworm

Caenorhabditis elegans

• One of the best characterized multicellular animal at the level of genomics, genetics, embryology

• Its genome is fully sequenced

C. elegans

has a full set of organ systems, has complex sensory systems, shows coordinated behavior, and it is possible to trace the lineage of every one of its approximately 1000 constituent cells

C. elegans

Could be male only or hermaphrodite [have both female and male reproductive organs, but they are not female or male only]

C. elegans

Have short life cycle of 2 weeks

C. elegans Life Cycle and Research

Its provides models for many human diseases including neurological disorders, congenital heart diseases and kidney diseases, studying apoptosis, could hold the key in counteracting aging of humans, can provide clues in cancer, diabetes, and other diseases.

FRUIT FLY (Drosophila melanogaster

A versatile model organism that has been used extensively for biomedical research.

Fruitfly

biological complexity comparable to that of a mammal

Fruitfly

Study specific diseases; mutant genes have been discovered in ___ that produces phenotypes with abnormalities with the nervous system [abnormal brain structure, adult on-set degeneration of nervous system, retinal degeneration (retinitis pigmentosa)]

Huntington disease

[rare inherited disease that causes the degeneration of nerve cells in the brain],

Machado-Joseph Disease or Spinocerebellar Ataxia Type III

[rare inherited ataxia or lack of muscular control which affect the central nervous system and characterized by slow generation of the hind brain],

Myotonic dystrophy

[characterized by progressive muscle wasting and weakness; can prolonged muscle contractions or myotonia and are not able to relax certain muscles after use],

Alzheimer’s disease

[neurologic disorder that causes the brain to shrink and brain cells to die]

8-14 days

life cyle of fruitfly

Danio rerio (ZEBRA FISH)

Small size, short life cycle, ease of culture, and ability to readily produce mutations relevant to human health and disease

Zebra fish

48hrs is enough for the development of most of the organ systems.

Zebra fish

The embryonic development can be seen through its transparent egg and closely resembles that of higher vertebrates

Zebra fish

Used to study vertebrate development

• Reproduces rapidly

• Development in ex vivo.

• Entire initial development is transparent.

Chick embryo

provides an excellent model system for studying the development of higher vertebrates wherein growth accompanies morphogenesis.

Chick Embryo

Can be used to observe GFP

(Green Fluorescent Protein) – known as the Roslin Green or Cytoplasmic GFP

Powerful tool for developmental biology, facilitating fate mapping, cell lineage, and tissue grafting

Gallus gallus domesticus

Chick embryo

MOUSE (Mus musculus)

Closest mammalian model organism to humans

Adult mice:

reproduce quickly, as often as 3 weeks

MOUSE (Mus musculus)

has already proven extremely useful in development, genetic, and immunology studies

• Transgenics and KO's possible

• A great system for studying and understanding human disease, as well as a mechanism for investigating new treatment strategies in ways that cannot be done in humans

KNOCK OUT MICE

A mouse that has one or more genes which have been turned off

Arabidopsis thaliana (Thale cress or Rock cress)

MUSTART PLANT

Arabidopsis thaliana

Small flowering plant with white flowers (often considered as a week)

Arabidopsis thaliana

Named as the ‘premiere model for plant biology’

• Has a small genome relative to other plants and is easily grown under laboratory conditions

• Amenable to some genetics particularly generation of transgenics

Loci or locus

Refers to the mapping of genes to specific locations on chromosomes

clone genes, especially disease genes

The ultimate goal of gene mapping is to ___

Genetic Mapping
Physical Mapping

2 Types of Gene Mapping

Genetic Mapping

using linkage analysis to determine the relative position between two genes on a chromosome

Physical Mapping

– using all available techniques or information to determine the absolute position of a gene on a chromosome

Linkage analysis

is the genetic mapping that is based on the linkage between “loci” or the locations of genes

centimorgan

The distance between genes is called

Recombinant DNA

Can be done in-vitro. Once made, the recombinant DNA molecules are introduced in an organism (often bacterium)

Restriction enzyme

enzymes are produced by bacteria as a defense mechanism against infection from viruses.

Prevent viral infection by degrading the DNA of viruses

DNA ligation by ligase

Seal the phosphodiester backbone of the DNA to covalently join the fragments together to form the recombinant DNA molecules

Restriction enzyme

– recognizes and binds to DNA at a specific nucleotide sequence [restriction site]

palindrome

Most recognition sequences often exhibited a form

of symmetry described as a ___

Alu-1

known as blunt ends

DNA Cloning Vectors

DNA molecules that accept DNA fragments and replicate inserted DNA fragments when vectors are placed into host cells

DNA cloning

is done by inserting a particular fragment of DNA in a purified DNA genome of a self-replicating genetic element (plasmid)