The chicken is closer to man than the mouse

Genetics / The genetic changes that go through the mouse are faster than those that went through the human and the chicken

by Tamara Traubman

About 300 million years ago, the ancestor of

The lineages from which man, the mouse and the chicken evolved, over years of

evolution. Now Dr. David Brett and his colleagues from the Roslin Institute have discovered,

The home of Dolly the Sheep, because from the moment the three split from the same ancestor,

The genome of the mouse has changed at a much faster rate than that of man and

the chicken In the last tens of millions of years, the pace of changes has been

In the genome of the rodent lineage, extremely fast. The rapid rate of genetic change

of the mouse, he genetically distanced it from the human and the chicken, which he slaughtered

Their genetic change is relatively slow. while the mouse chromosomes

Reorganized on average once in a million years, in this person's family

Happens once in two million years, and with chickens about once in five

A million years.

This phenomenon was discovered through the investigation of segments in the genetic maps of three

the offspring A genetic map shows the relative position of the genes along the length

the chromosome. Each gene has an original place in the chromosome, but the order of the genes is on

The top of the chromosomes can change. For example, a series of genes that appeared in the section

The upper part of the chromosome can "jump" and move to its lower part, or

even to another chromosome.

The researchers examined sections of the genetic maps, which contain shared genes

For a man, a mouse and a chicken, and check how often such a section changes

Its place in the chromosome. Their research is published today in the scientific journal "Nature".

Apparently, the human genetic map should have been closer to the map

of the mouse, because both are mammals. "We know that all rodents

We are undergoing a very rapid evolution, in all respects," says Dan Graor,

Professor of Molecular Evolution at Tel Aviv University. He adds that

Molecularly, Homo sapiens is the most primitive mammal.

"From this point of view, humans are fossils, we are undergoing evolution

very slow. And now it turns out that it's the same with the chicken."

The rate of occurrence of changes in the genome improves the survivability of my husband

Haim. The mutation rate of bacteria, for example, is very fast, and this is one

The reasons that humans find it so difficult to overcome. But it is still not clear

How, if at all, is the reorganization of the gene order on the chromosome,

affects the rest of evolution.

When scientists want to test how new substances behave in the body, they

This is done first in mice and other rodents. The new study does not bring

With it new news for mice - they will continue to be used as research tools in the meantime

the ideal. Their life cycle is relatively short and allows for quick testing

Changes, which in other mammals last several decades. observes

Anatomically, the mice are closer to humans than the chicken. Still

No research has been done on the matter, but it is possible that relative to the chickens, they have too

A greater number of genes, which are similar to those of humans.

{Appeared in Haaretz newspaper, 25/11/1999

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