Tuesday, April 29, 2008

Fruit Fly 2


This is a picture of DNA stretched out (it normally looks like a twisted ladder). Don't worry if you can't understand the technical words. Just realize this is the way organisms carry genes--the features which are passed onto offspring. The DNA also is what is used to make the protein. It acts as a code. The bars in the middle come apart and they are "read" by another molecule, the RNA, to produce a mirror-image template. This template moves on to another part of the cell to eventually be read again. This time, the reading leads to new proteins.

The bars in the middle of the DNA are known as "base pairs." DNA has four different molecules that can be used as base pairs--two linked to each other along the rungs of the ladder. The reading is done by splitting DNA the long way and translating code of the four molecules in combinations of three that run along the length of the template. A new molecule of RNA is made and that is further processed to make protein. For example, a CGA will eventually be read as the amino acid "Arginine." That will be a part of the protein which is made by putting the amino acids together in correct order.The fruit fly has 180 million base pairs. After division and recombination through egg and sperm, they are passed along to individuals of the next generation which will once again have 180 million base pairs.

A description of the fruit fly from a website named "FlyBase" is in the links at right. The fruit fly has two life forms, the larva and the adult. There are also developments through embryo and pupa stages. The larva gets a shell around it as it metamorphosizes to the adult. The micro-processes by which it develops are being discovered. They are important and fit in with the discoveries of the genes and how they work.

It was previously thought that each gene translates into one protein in the organism. To remind you very briefly, sections of the DNA are divided into specific genes. The great surprise from the Human Genome Project is there are less genes than proteins. For example, there are only about 25-30 thousand genes in humans. There are around 100 thousand proteins, and these have further modifications done to them in the cell so that there are an estimated one million types of proteins in the human body.

The modifications to proteins in organisms come both before and after these proteins are made. There are differences between species, and I'll be talking about a variety of species, not just the fruit fly.

You have probably heard in the media that human and monkey DNA are very similar (varying reports of 95-99%). However, humans and monkeys are not 95% similar. A great deal of the differences are now being discovered in the regulatory levels of the genes. There are areas in DNA which had been called "junk DNA." These are between the genes and were thought to have little activity. Now they are thought to have regulatory affects on protein production.

As for the fruit fly, it is going to be an interesting study in how all these factors work together in an amazingly complex way.

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