Siyapath
Sign up

Lesson: Chapter 6 — The Structure and Function of Plant and Animal Cells

6.5. Cell growth and cell division 2 of 3

What cell division is

Cells can multiply as well as grow. One cell can become two, then four, then eight, and so on. Cells multiply by cell division.

Cell division

Cell division is the process by which the cellular material of a cell is divided so that new cells are formed.

The order matters

For cell division to be complete in a true nucleated cell, the nucleus must divide first and the cytoplasm must divide afterwards.

The chromosomes start to show

Before nuclear division, the chromosomes within the nucleus — which carry the genetic material that passes inherited characteristics from one generation to the next — begin to become clearly visible.

Figure to be added

Figure 6.17 — how the chromosomes appear as fine threads in the nucleus of an ordinary cell, and how they appear in a cell that has begun to divide, with each chromosome separated into chromatids.

Observation

In an ordinary cell the chromosomes are seen as fine, thread-like chromatin. As division begins they thicken, and each chromosome shows up clearly as having separated into two chromatids.

Chromosomes are not newly made

Chromosomes do not "appear" at division — they were in the nucleus all along, and that is simply when they condense enough to be seen. Chromatin and chromosomes are one material in two states.