Glossary
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| Term | Definition |
|---|---|
| Telomerase | An enzyme that adds specific DNA sequence repeats ("TTAGGG" in all vertebrates) to the 3' ("three prime") end of DNA strands in the telomere regions at the ends of chromosomes. It counteracts chromosome shortening which is a molcular consequence of the cellular replication machinery of the linear eukaryotic chromosomes. The enzyme is a reverse transcriptase that carries its own RNA template; this RNA is used as a template for eukaryotic DNA replication. [Wikipedia entry] |
| Telomere | A region of highly repetitive DNA at the ends of a linear chromosome that functions as a disposable-DNA buffer for sequence loss during replication. Telomerase counteracts the sequence loss. When telomeres incidentially get too short, cells stop dividing and become senescent. [Wikipedia entry] |
| Therapeutic cloning | Involves taking an egg from which the nucleus has been removed, and replacing that nucleus with DNA from the cell of another organism resulting in a blastocyst (an early stage embryo with about 100 cells) with almost identical DNA to the original organism. [Wikipedia entry] |
| Thymine | A pyrimidine nucleobase. Thymine is found as building block in the nucleic acid DNA. In RNA thymine is replaced with uracil. Thymine always base pairs with adenine. [Wikipedia entry] |
| Tissue rejection | Failure of transplantation that occurs when an organism recognizes transplanted tissue as foreign, and mounts an immune response. [Wikipedia entry] |
| Totipotency | The ability of a single cell, usually a stem cell, to divide and produce all the differentiated cells in an organism. [Wikipedia entry] |
| Trait | Trait or character is a feature of an organism. The term phenotype is sometimes used as a synonym for trait in common use, but strictly speaking, does not indicate the trait, but the state of that trait (e.g., the trait eye colour has the phenotypes blue, brown and hazel). [Wikipedia entry] |
| Transcribe | Make complementary RNA from the information of the coding strand of DNA. [Wikipedia entry] |
| Transcription factor | (TF) Protein that regulates the activation of transcription in the eukaryotic nucleus. Transcription factors localise to regions of promoter and enhancer sequence elements either through direct binding to DNA or through binding other DNA-bound proteins. They act by promoting the formation of the preinitiation complex (PIC) that recruits and activates RNA polymerase. [Wikipedia entry] |
| Transcriptional silencing | Gene silencing by inhibition of transcription (compare posttranscriptional gene silencing). [Wikipedia entry] |
| Transdifferentiation | Takes place when a non-stem cell transforms into a different type of cell, or when an already differentiated stem cell creates cells outside its already established differentiation. [Wikipedia entry] |
| Transgene | A transgene is a gene or genetic material which has been transferred by any of a number of genetic engineering techniques from one organism to another. [Wikipedia entry] |
| Transgenic | A genetically modified organism (GMO) whose genetic material has been altered using techniques known as recombinant DNA technology. [Wikipedia entry] |
| Transposable element | (= transposon) Sequences of DNA that move around to different positions within the genome of a single cell. The process is called transposition. DNA transposons move by a cut and paste mechanism, while plicative transposons usually move via RNA intermediates. [Wikipedia entry] |
| Trithorax-group proteins | A family of proteins that remodel chromatin such that transcription factors can bind to promoter sequences in DNA, switching genes on. In Drosophila, the Trithorax-group (trxG) and Polycomb-group (PcG) proteins act antagonistically and interact with chromosomal elements, termed Cellular Memory Modules (CMMs). [Wikipedia entry] |
