APPENDIX I 



Time Limit, limitation of time available for zygotene pairing which 

 causes LocaHzation. Darlington 1935. 



Torsion Pairing, v. Pairing. 



Trabant, SateUite. 



Trait, Character. 



Transgressive Segregation, the appearance in a segregating generation 

 (Fg, backcross, etc.) of an individual or individuals falling outside 

 the limits of variation set by the parents and Fj of the cross in one 

 or more characters. Cf. Heterosis. 



Translocation, change in position of a segment of a chromosome to 

 another part of the same or of a different chromosome, especially 

 non-reciprocally in which case the segment is always interstitial, 

 V. Structural Change. Bridges 19 17. 

 Reciprocal (or Mutual) Translocation, Interchange. 



Trigenic, v. Monogenic. 



Trihybrid, Trigenic Hybrid. 



Triplex, v. Nulliplex. 



Triploid, f . Diploid, Polyploid. 



Triplo-Polyploid, a relatively triploid derivative of an allopolyploid. 

 Janaki Ammal 1941. 



Trisomic, v. Polysomic. Blakeske 1921. 



Secondary Trisomic, a trisomic individual in which the extra chromo- 

 some has two identical ends (and is probably an Isochromosome). 

 Belling 1927. 

 Tertiary Trisomic, a trisomic individual in which the extra chromo- 

 some is the product of interchange between two standard chromo- 

 somes. Belling 1927. 



Trivalent, v. Univalent. 



Twins, two embryos developed simultaneously within one uterus in 

 mammals, within one vitelline membrane in other vertebrates or 

 within one testa in phanerogams. Similarly Triplets, Quadruplets, 

 etc., V. also Dizygotic, Monozygotic, Polyembryony. 



Unhxable, Ever-sporting from seed. 

 Unilateral Inheritance, v. Inheritance. 

 Unisexuality, v. Dioecy. 



Unit Character, one whose difference from an alternative is transmitted 

 as a unit in heredity. Cf. Character, Factor, Gene. 



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