Centromere is a part of chromosome, where both chromatids of chromosome attached to each other, spindle fibres during cell division, attached to centromere.
Ribosome is a membraneless cell organelle made up of RNA and protein. Ribosome helps in protein synthesis.
Lysosome is a single membrane bound cell organelles which helps in intracellular digestion.
Gene is a unit of heredity composed of DNA molecules.