5.12 -Centrosome and Centrioles AND Nucleus

2. Both the centrioles in a centrosome lie ........ to each other in which each has an organisation like the ........
6. The centrioles form the basal body of cilia or flagella, and .......... that give rise to spindle apparatus during cell division in animal cells.
11. Later the material of the nucleus stained by the basic dyes was given the name chromatin by ...........
13. Electron microscopy has revealed that the nuclear envelope, which consists of two parallel membranes with a space between (10 to 50 nm) called the ..........., forms a barrier between the materials present inside the nucleus and that of the cytoplasm.
14. The central part of the proximal region of the centriole is also proteinaceous and called the ....... , which is connected with tubules of the peripheral triplets by radial spokes made of protein.
15. They are made up of nine evenly spaced peripheral fibrils of tubulin protein. Each of the peripheral fibril is a ......... .
20. Centrosome is an organelle usually containing two cylindrical structures called ................
21. They are surrounded by amorphous ......... materials.
22. The outer membrane usually remains continuous with the ................ and also bears ribosomes on it.
23. The content of nucleolus is continuous with the rest of the nucleoplasm as it is not a ............. structure.

1. Nucleus as a cell organelle was first described by .......... as early as 1831.
3. These nuclear pores are the passages through which movement of ....... and ........ molecules takes place in both directions between the nucleus and the cytoplasm.
4. The nuclear matrix or the nucleoplasm contains ............ and ...........
5. The interphase nucleus (nucleus of a cell when it is not dividing) has highly extended and elaborate nucleoprotein fibres called ..........., nuclear matrix and one or more spherical bodies called nucleoli (sing.: nucleolus)
7. Some mature cells even lack nucleus, e.g., ..............of many mammals and .......... cells of vascular plants.
8. Normally, there is only .......... per cell, variations in the number of nuclei are also frequently observed.
9. The nucleoli are .......... structures present in the nucleoplasm.
10. The ............ nucleus has a loose and indistinct network of nucleoprotein fibres called chromatin.
12. At a number of places the ............. is interrupted by minute pores, which are formed by the fusion of its two membranes.
16. Larger and more numerous nucleoli are present in cells actively carrying out .............
17. But during different stages of ............, cells show structured chromosomes in place of the nucleus.
18. Nucleolus is a site for active ......... synthesis.
19. The ........ triplets are also linked.