Biomaterial Database

Accumulation of spontaneous mutations in the ciliate Tetrahymena thermophila. 2013

Hong-An Long, and Tiago Paixão, and Ricardo B R Azevedo, and Rebecca A Zufall

Department of Biology and Biochemistry, University of Houston, Houston, Texas 77204-5001.

Knowledge of the rate and fitness effects of mutations is essential for understanding the process of evolution. Mutations are inherently difficult to study because they are rare and are frequently eliminated by natural selection. In the ciliate Tetrahymena thermophila, mutations can accumulate in the germline genome without being exposed to selection. We have conducted a mutation accumulation (MA) experiment in this species. Assuming that all mutations are deleterious and have the same effect, we estimate that the deleterious mutation rate per haploid germline genome per generation is U=0.0047 (95% credible interval: 0.0015, 0.0125), and that germline mutations decrease fitness by s=11% when expressed in a homozygous state (95% CI: 4.4%, 27%). We also estimate that deleterious mutations are partially recessive on average (h=0.26; 95% CI: -0.022, 0.62) and that the rate of lethal mutations is <10% of the deleterious mutation rate. Comparisons between the observed evolutionary responses in the germline and somatic genomes and the results from individual-based simulations of MA suggest that the two genomes have similar mutational parameters. These are the first estimates of the deleterious mutation rate and fitness effects from the eukaryotic supergroup Chromalveolata and are within the range of those of other eukaryotes.

UI	MeSH Term	Description	Entries
D009154	Mutation	Any detectable and heritable change in the genetic material that causes a change in the GENOTYPE and which is transmitted to daughter cells and to succeeding generations.	Mutations
D006720	Homozygote	An individual in which both alleles at a given locus are identical.	Homozygotes
D012641	Selection, Genetic	Differential and non-random reproduction of different genotypes, operating to alter the gene frequencies within a population.	Natural Selection,Genetic Selection,Selection, Natural
D016678	Genome	The genetic complement of an organism, including all of its GENES, as represented in its DNA, or in some cases, its RNA.	Genomes
D016808	Tetrahymena thermophila	A species of ciliate protozoa used in genetic and cytological research.	Tetrahymena thermophilas,thermophilas, Tetrahymena
D017384	Sequence Deletion	Deletion of sequences of nucleic acids from the genetic material of an individual.	Deletion Mutation,Deletion Mutations,Deletion, Sequence,Deletions, Sequence,Mutation, Deletion,Mutations, Deletion,Sequence Deletions
D056084	Genetic Fitness	The capability of an organism to survive and reproduce. The phenotypic expression of the genotype in a particular environment determines how genetically fit an organism will be.	Darwinian Fitness,Reproductive Fitness,Fitness, Darwinian,Fitness, Genetic,Fitness, Reproductive
D056890	Eukaryota	One of the three domains of life (the others being BACTERIA and ARCHAEA), also called Eukarya. These are organisms whose cells are enclosed in membranes and possess a nucleus. They comprise almost all multicellular and many unicellular organisms, and are traditionally divided into groups (sometimes called kingdoms) including ANIMALS; PLANTS; FUNGI; and various algae and other taxa that were previously part of the old kingdom Protista.	Eukaryotes,Eucarya,Eukarya,Eukaryotas,Eukaryote
D059645	Mutation Rate	The number of mutations that occur in a specific sequence, GENE, or GENOME over a specified period of time such as years, CELL DIVISIONS, or generations.	Mutation Frequency,Frequencies, Mutation,Frequency, Mutation,Mutation Frequencies,Mutation Rates,Rate, Mutation,Rates, Mutation
D018095	Germ-Line Mutation	Any detectable and heritable alteration in the lineage of germ cells. Mutations in these cells (i.e., "generative" cells ancestral to the gametes) are transmitted to progeny while those in somatic cells are not.	Mutation, Germ-Line,Germline Mutation,Germ Line Mutation,Germ-Line Mutations,Germline Mutations,Mutation, Germ Line,Mutation, Germline,Mutations, Germ-Line,Mutations, Germline