TAQ polymerase: DNA polymerase enzyme from the bacterium Thermus aquaticus (hence the TAQ); a thermostable enzyme widely used in PCR, optimum temp about 72 degrees C

Taxonomy: The very exciting science of classification.

​Test cross: Cross with a homozygous recessive (aa) to find out if an individual is AA or Aa

Thermostable enzyme: Active across a range of temperatures, not denatured at the usual 50/60oC. From thermophilic (heat loving) bacteria in hot springs e.g. TAQ polymerase. 

Tissue Fluid: Fluid which surrounds all cells and is similar to plasma without the plasma proteins. Cells obtain nutrients from the tissue fluid and deposit cellular waste (urea and CO2).

Tracheids: the main conducting cell of the xylem, characterized by an elongated shape and lignified secondary cell wall. See also vessel element. 

Transcription: First step in protein synthesis, basically ‘gene copying’. Involves transferring the genetic code from DNA to mRNA. Happens in the nucleus.

Transfer RNA [tRNA]: a molecule that brings specific amino acids to ribosomes. Clover leaf shaped, has an anticodon on one end & carries an amino acid at the other.

Transgenic organism: An organisms whose DNA has been altered, such as the bacteria with human genes inserted

Translation: Second step in protein synthesis. Using the code on the mRNAto build a protein. Takes place on ribosomes

Translocation: The movement of the products of photosynthesis (sucrose, amino acids etc) throughout a plant in phloem tissue. The driving force behind translocation is called the mass flow hypothesis, or Munch’s theorem. 

Transpiration stream: the passage of water through the plant from roots to leaves and out into the atmosphere.

Transpiration: Loss of water vapour from the plant’s upper surfaces, mainly leaves.

True breeding: Homozygous individuals which always produce offspring on the same type.