T-chromosome — 147 — Tester Strain 



Telomere. — (i) A gene situated at the end of a chromosome. 



(ii) A chromosome end. 

 Telomitic. — (Of chromosomes) with terminally attached 



spindle fibres; having the centromere terminal. 

 Telophase. — The last stage in cell division before the nucleus 



returns to the resting phase. See Mitosis; Meiosis. 

 Telosynapsis. — The end-to-end association of chromosomes 



•sometimes seen at zygotene ; telosyndesis. 

 Telosyndesis. — Telosynapsis, q.v. 

 Teratism. — Morphological or anatomical abnormality. 

 Teratology. — The study of morphological or anatomical ab- 

 normalities (especially malformations or monstrosities). 

 Terminal Affinity. — The property by which chromosomes are 



held together end to end from diplotene till metaphase or 



brought together in this way at metaphase (Darlington). 

 Terminal Chiasma. — A chiasma, or physical exchange of 



partners, which occurs at the extremity of the chromatids. 

 Terminal Gene. — A gene situated at the extreme end of a 



chromosome ; telomere. 

 Terminal Granules. — Granular bodies which occur at the 



ends of some of the chromosomes in certain plant species. 



These granules should not be confused with satellites. 

 Terminal Trabant. — See Trabant. 

 Terminalization. — Expansion of the association of the two 



pairs of chromatids on one side of a chiasma at the expense 



of that on the other side. So called because the resulting 



"movement" of the chiasma is usually, if not always, towards 



the ends of chromosomes. Arrest o£ . Stoppage of the 



movement of a chiasma, through the opposite segments distal 



to it being non-homologous (Darlington). 

 Terminalization Coefficient. — The number of terminal chias- 



mata divided by the total number of chiasmata. 

 Territoriality. — Persistent attachment to a specific small 



territory. 

 Tertiary Mutant. — A tertiary trisomic. See Trisomic. 

 Tertiary Split. — Longitudinal doubleness of the chromonema 



of each chromatid which may become visible during the first 



or second division of meiosis. 

 Testcross. — A cross between a heterozygote and a recessive 



homozygote. 

 Tester Strain. — A strain whose genetic make-up is such that 



its contribution to the inheritance of the ofifspring will not hide 



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