# Structural Biochemistry/Model Organisms

A model organism is an indispensable tool used for medical research. Scientists use organisms to investigate questions about living systems that cannot be studied in any other way. These models allow scientists to compare creatures that are different in structures, but share similarities in body chemistry. Even organisms that do not have a structural body, such as yeast and mold, can be useful in providing incites to how tissues and organs work in the human body. This is because enzymes used in metabolism and the processing of nutrients are similar in all living things. Other reasons model organisms are useful are that they are simple, inexpensive, and easy to work with.
Examples of model organisms:

## Escherichia Coli: Bacterium

There are good and bad bacteria. The one form of bacterium one is usually familiar with is the E. coli that is associated with tainted hamburger meat. However, there also exist "non-disease-causing" strains of E. coli. in the intestinal tracts of humans and animals. These bacteria are the main source in providing vitamins K and B-complex. They also help in the digestive system and provide protection against harmful bacteria. Differentiating between harmful and helpful strains of E. coli can help distinguish the genetic differences between bacteria in humans and bacteria that cause poisoning.

## Dictyostelium Discoideum (Dicty): Amoeba

Amoeba is microscopic cell which is 100,000 times smaller than a grain of sand. This organism has between 8,000 and 10,000 genes and many of them are similar to those in humans and other animals. Dicty cells usually grow independently. However, with limited food resources, these cells can pile on top on each other to form a multicelled structure of up to 100,000 cells. When migrating, this slug-like organism will leave behind a trail of slime. They can disperse spores that are capable of generating new amoeba.

## Neurospora Crassa: Bread Mold

This type of model organism is used world wide in genetic research. Researchers like to use bread mold because it is easy to grow and can answer questions about how species adapt to different environments. Neurospora is also useful in the studying of sleep cycles and rhythms of life.

## Saccharomyces Cerevisiae: Yeast

Yeast is commonly used in research, but it is also an important part of life outside the laboratory. It is a fungus and has eukaryote properties. Researchers prefer yeast because it is fast to grow, cheap and safe to use, and easy to work with. Yeast can be used as a host for mammalian genes, and it allows scientists to study how they function inside the host. Discoveries of the antibiotic penicillin or the protein called sirtuin that interferes with aging resulted from observing fungus.

## Arabidopsis Thaliana: Mustard Plant

Arabidopsis is a flowering plant that is related to cabbage and mustard. Researchers often use this plant to study plant growth because it has very similar genes with other flowering plants and little encoded-protein DNA, which makes it easy to study genes. Arabidopsis has eukaryotic cells, and the plant can mature quickly in six weeks. Cell communication in plants operates much like human cells do, and this makes it easier to study genetics.

## Caenorhabditis Elegans: Roundworm

Roundworms are as tiny as the head of a pin, and they live in dirt. In the laboratory, they live in petri dishes and feed on bacteria. This C. elegans creature has 959 cells and one third of the cells form the nervous system. Researchers like to use roundworm because it is transparent, which allows a clear view of what goes on in the body. C. elegans has more than 19,000 genes compare to a human of about 25,000 genes. C. elegans is the first animal genome to be decoded, and the major of the genes is similar to that of humans and other organisms.

## Drosophila Melanogaster: Fruit Fly

This type of fruit fly is most commonly used in research. Fruit flies in the laboratory are often exposed to harmful chemicals and radiation that can change their DNA sequences. Researchers allow flies to mate and then study their offspring for mutations. The mutant flies help researchers to study detective genes. Fruit flies can reproduce quickly, which makes it easy to create mutant flies, and this enables researchers to study how genes function. By relating some of the defects found in fruit flies with those in humans, researchers may discover the defective genes as well.

## Danio Rerio: Zebrafish

Zebrafish habitat in slow streams, rice paddies, and the Ganges River in East India and Burma. They are also found in pet stores. Researches prefer zebrafish because their eggs and embryos are transparent, which provide a plain view of the development process. It takes only 2 to 4 days for zebrafish cells to divide and form the fish's body parts: eyes, heart, liver, and etc. This research enables scientists to study birth defects, the proper development of the heart and blood.

## Mus Musculus: Mouse

Mice are mammals like humans, and we share 85 percent of our genes. Because mice are very similar to people, they are used to study diseases in humans. Scientists can create "knockout" mice, missing gene mice, and study how the mice function.

## Rattus Norvegicus: Rat

Rat was the first animal to be used in scientific research. For the most part, laboratory rats are used to test drugs and most of what we know about cancer started with rat research. Rats are mammals and are bigger than most model organisms, which makes it easy for scientists to perform experiments on the rat brain. Scientists have learned about substance abuse and addiction, learning and memory, and neurological diseases through rats. They are also useful in the studying of asthma, lung injury, and arthritis disease.

## Pan Troglodytes: Chimpanzee

The fact that chimpanzees share 99 percent of the genes with humans makes them very unique for studying human genome. Because they are immune to malaria or AIDS, ongoing medical research is trying to discover the reason at genomic level.

## Lambda Phage: Virus

A lambda phage is a bacterial virus, or bacteriophage that infects a bacterial species such as escherichia coli. This virus has a temperate lifestyle meaning that it may well reside within the genome of its host until its lyses out of its host, also known as lysogeny. The lambda phage consists of constituent parts that all take part in its integration in the host genome. The phage contains a capsid head, a tail, and tail fibers for which is used to latch on to its host. The importance of this model organism to scientists is its ability to incorporate itself into its hosts genome allowing to integrate its genomic DNA into its host. This is especially helpful to scientists for genomic work.

## Chlamydomonas reinhardtii: Green Algae

This model organism is a unicellular green algae that is primarily used to study the mechanisms of photosynthesis, regulation of metabolism, cell to cell recognition, adhesion, response to nutrient deprivation and flagella motility. It proves to have a great significance to scientists because it can grow in media lacking organic carbon and chemical energy sources. In addition this model organisms is associated with fluorescence and can grow in the dark when supplied with other unicellular green algae as a source of hydrogen.

## Reference

The New Genetics. National Institute of General Medical Sciences. Revised October 2006. http://publications.nigms.nih.gov/thenewgenetics.