27 May 2009

Mouse genes and human diseases

Mouse genes turned out to be more human
Three-quarters of mouse genes may be useful for studying human diseasesAlexey Timoshenko, GZT.RU

Scientists from ten different research centers in the USA, Great Britain and Sweden have announced the successful reconstruction of the mouse genetic code. Their report in the journal PLoS Biology means the completion of the most important work: now doctors around the world will be able to create much more accurate and reliable tools for studying the causes of diseases, and biologists will have the opportunity to explore fundamental questions about how the mammalian body as a whole works.

The breakthrough in biology was provided by mutant miceMice with purposefully altered genetic code have already caused a revolution in medical and biological science, and a revolution comparable to the appearance of X-rays or even a microscope.

The term "bred" is not even applicable to such mice. Transgenic animals are created purposefully. A new gene is inserted into the DNA of a fertilized egg or an existing one is cut out of it. Biologists have already obtained mice carrying genes associated with Alzheimer's disease, mice with genetically determined obesity and mice with a predisposition to cancerous tumors. There are even mice that not only have a high probability of forming cancerous tumors, but each tumor cell synthesizes a fluorescent label to search for metastases at the earliest stage of their growth.
Mice are relatively unpretentious, multiply quickly, and working with them does not cause such ethical objections as working with monkeys. There are lines (as scientists call "breeds" of animals obtained by closely related crossing) of rodents deprived of immunity – such are kept in sterile rooms.

At the same time, mice are quite close to humans in terms of anatomy and physiology: even senile dementia or long-term memory disorders can be studied quite effectively on them. 

Read and understandDNA is a molecule made up of individual nucleotides, basic blocks of four different types.

The sequence of nucleotides can be established, such a procedure is called reading, or sequencing (from the English sequence – sequence) of the genome. Scientists have learned to carry out this procedure for a long time and have read not only the mouse, but also the human genome. Primitive against their background (only 8 genes), the genetic code of the A/ H1N1 virus is read at all regularly: this allows you to quickly monitor whether a mutation of the "swine" flu has occurred.

But just reading the sequence is not enough, it also needs to be understood. Biologists analyzed the mouse genome read earlier and counted 20210 genes encoding different proteins. A person, oddly enough, has fewer such genes: only 19042. What genes a mouse differs from a human and why a rodent weighing less than 30 grams has more of them is a separate question that researchers were looking for an answer to.

How does a mouse differ from a human?Biologists have identified 3,767 genes that distinguish a mouse from a human, and over a thousand such genes have been found for the first time.

This knowledge is especially valuable for creating rodents on which certain diseases will be studied: doctors will be able to distinguish "mouse" genes from those common to all mammals. In addition, scientists were able to solve some of the riddles associated with repetitive sections of the genome. Duplicates of genes arose during the evolutionary development of rodents.

It was such repeats that eventually led to the appearance of new genes, and it was by repeats that scientists explained the larger size of the mouse genome compared to the human one. Moreover, biologists have even identified what the repeating genes are responsible for.

The reconstruction of the history of genetic changes carried out by scientists has shown that a significant part of such genes is associated with the recognition of odors and appeared within the last ten million years. Mice and most rodents have poor eyesight, but a great sense of smell.

Biologists have come to the conclusion that 75% of human and mouse genes coincide. This means that many diseases can be studied on rodents, and knowledge about specific genes will allow you to create transgenic animals faster and carry out more complex manipulations with them.

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