A Basic Introduction to the Science Underlying NCBI Resources
WHAT IS A GENOME?
Life is specified by genomes. Every organism, including humans, has a genome that contains all of the biological information needed to build and maintain a living example of that organism. The biological information contained in a genome is encoded in its deoxyribonucleic acid (DNA) and is divided into discrete units called genes. Genes code for proteins that attach to the genome at the appropriate positions and switch on a series of reactions called gene expression.
"BERKELEY, CA (KGO) -- At UC Berkeley, there is new hope for some of mankind's biggest maladies from research about the smallest of creatures.
"What we have found is fundamental," Simon Prochnik, a bioinformaticist at the DOE Joint Genome Institute, said.
Prochnik studies the genetic make-up of single celled amoebas. He and a team of researchers have now sequenced the genome of a strange, single-celled organism called Naegleria gruberi. They say it is very similar to the most fundamental and early life that existed on Earth 1 billion years ago.
"Organisms like this would be all that existed on this planet, back then," Procnik said. "This is the first time we have been able to model how early creatures came about."
Naegleria gruberi is uniquely sophisticated and complicated. It swims to food and away from stress. It changes forms depending upon the environment. It has a basic amoeba form, a flagellating form and in difficult conditions, can turn into a hard-shelled cyst.
The more we understand about how amoebas function and move, the more they tell us about own make-up. Amoebas play a large role in human immunity through white blood cells. We also find them in the lungs, the kidneys, and of course, in human sperm cells, which sometimes malfunction, leading to sterility. In development, flagella also play an important part in making sure the layout of the human body happens properly.
"Biologists have been estimating the size of genomes for decades. In 1971, for example, researchers reported that a species of Italian bat, Miniopterus, has a genome half the size of the human genome. Similarly, the genome of Muntiacus, a species of Asian barking deer, was estimated at about 70 percent of that of humans. As reported this week, the human genome contains about 3 billion chemical units of DNA, or base pairs.
In the animal kingdom, the relationship between genome size and evolutionary status is not clear. One of the largest genomes belongs to a very small creature, Amoeba dubia. This protozoan genome has 670 billion units of DNA, or base pairs. The genome of a cousin, Amoeba proteus, has a mere 290 billion base pairs, making it 100 times larger than the human genome. |
