X
- X chromosomeSex chromosome present in both sexes in the XY and X0 sex-determination systems
- X-galX-gal (also abbreviated BCIG for 5-bromo-4-chloro-3-indolyl-β-D-galactopyranoside) is an o
- X-inactivationInactivation of copies of X chromosome
- X-linked dominant inheritanceMode of inheritance
- X-linked recessive inheritanceMode of inheritance
- X-linked spinal muscular atrophy type 2X-linked spinal muscular atrophy type 2 (SMAX2, XLSMA), also known as arthrogryposis multi
- Xanthomonas campestris pv. campestrisBacterial variant causing black rot
- Xanthomonas oryzae pv. oryzaeVariety of bacteria
- XDNABenzo-homologated DNA analogue
- XenobiologyScience of synthetic life forms
- XenobioticForeign chemical substance found within an organism
- XenophyophoreaClade of single-celled organisms
- XenotransplantationTransplantation of cells or tissue across species
- XerophthalmiaXerophthalmia (from Ancient Greek xērós (ξηρός) meaning "dry" and ophthalmos (οφθαλμός) me
- XerosereXerosere is a plant succession that is limited by water availability. It includes the diff
- Xiphoid processSmall bony extension of the lower part of the sternum
- XISTNon-coding RNA
- XO sex-determination systemBiological system that determines the sex of offspring
- Xq28Genetic marker at the lower tip of human X chromosome
- XY sex-determination systemMethod of determining sex
- XylanPlant cell wall polysaccharide
- Xylella fastidiosaBacteria harming plants, including crops
- XylemWater transport tissue in vascular plants
- XylosmaXylosma is a genus of flowering plants in the family Salicaceae. It contains around 100 sp
- XYY syndromeGenetic condition in which a male has an extra Y chromosome