Printer Friendly

Gene-code variety.

In this heyday of genetic engineering, scientists take great advantage of the uniformity of the DNA code. A human cell's gene, for example, once put in the proper context, can be effectively translated by the decoding equipment of a bacterium. But the genes of one group of organisms, single-celled animals called ciliates, are not translated well by the cellular machinery of other organisms. Now scientists report "the surprising finding" that the genetic coding of these simple animals actually departs from the so-called "universal" code. The only coding variations previously discovered are in genes of subcellular structures, the mitochondria (SNd9/15/79, p.185).

Stuart Horowitz and Martin A. Gorovsky of the University of Rochester in New York determined the nucleotide (DNA subunit) sequence of two genes in the nuclei of the ciliate. Tetrahymena thermophila. In the standard code, the sequence TAA is a "stop" signal, terminating the translation of a gene. But in these Tetrahymena genes, TAA corresponds to the amino acid glutamine.

Two groups of scientists report in the March 14 NATURE analyses of genes of another ciliate, Paramecium. Francois Caron and Eric Meyer of the National Center of Scientific Research in Gif-sur-Yvette, France, find that both TAA and TAG, which normally terminate gene translation, are scattered through the genes. Analysis of a specific Paramecium gene by J. R. Preer Jr. and colleagues at Indiana University in Bloomington indicates that TAA and TAG code for glutamine. In addition, work in West Germany indicates that TAA encodes glutamine in several genes in another ciliate, Stylonychia. In all these ciliates, only one of the usual stop codons, UGA, appears to act as a termination signal.

Under most conditions, any genetic change involving termination signals is likely to be lethal to an organism. A major puzzle now is how the variation in the genetic code of ciliates could have arisen during evolution.
COPYRIGHT 1985 Science Service, Inc.
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 1985, Gale Group. All rights reserved. Gale Group is a Thomson Corporation Company.

Article Details
Printer friendly Cite/link Email Feedback
Title Annotation:genetic coding of ciliates
Author:Miller, Julie Ann
Publication:Science News
Date:Mar 23, 1985
Words:310
Previous Article:Basins hasten brewing of oil.
Next Article:Serendipidity catches a supernova.
Topics:


Related Articles
Human genetic map: worth the effort?
Does nonsense DNA speak its own dialect?
COMMUNITIES BRIEFLY.
COMMUNITIES CALENDAR.
Who's really in charge? Physician assistants and nurse practitioners are common in health care facilities. But how much responsibility do they have?...
Cells' root: adult stem cells have a master gene.
Genesis meets the Big Bang and evolution, absent design.
Self-sacrificial love: evolutionary deception or theological reality?

Terms of use | Privacy policy | Copyright © 2020 Farlex, Inc. | Feedback | For webmasters