Chromosomes can be regarded as strings of genes arranged along their length, rather like beads on a thread. Each gene consists of a short section of the DNA that runs the full length of each chromoso]]> Almost all of the different types of cell in an individual contain the same genetic material in the chromosomes, as a consequence of mitosis. You had a glimpse of the appearance of the 46 human chromosomes in Figure 1.1, and in this unit we examine their size, shape and genetic composition.

Chromosomes can be regarded as strings of genes arranged along their length, rather like beads on a thread. Each gene consists of a short section of the DNA that runs the full length of each chromoso]]> In the final two sections of this unit, we shall look at some examples of endocytosis and exocytosis, in different types of cell. The molecules that are taken up or released by a cell and the triggers for secretion depend greatly on the type of cell, although the underlying transport processes are similar for many cell types, and relate to the systems described above.

The plasma membrane not only separates the cell interior from the extracellular environment, it also regulates and coord]]> In the final two sections of this unit, we shall look at some examples of endocytosis and exocytosis, in different types of cell. The molecules that are taken up or released by a cell and the triggers for secretion depend greatly on the type of cell, although the underlying transport processes are similar for many cell types, and relate to the systems described above.

The plasma membrane not only separates the cell interior from the extracellular environment, it also regulates and coord]]> Let us now return to the Fallopian tube, where a fertilized egg is assembling its chromosomes prior to commencing a series of mitotic divisions which will eventually give rise to the millions of cells that make up the human body. Obviously these millions of cells do not just exist as an amorphous mass: they are differentiated into many different types of cell, and they are organized into recognizable, discrete structures: tissues and organs. This is accomplished by a coordinated sequen]]> Let us now return to the Fallopian tube, where a fertilized egg is assembling its chromosomes prior to commencing a series of mitotic divisions which will eventually give rise to the millions of cells that make up the human body. Obviously these millions of cells do not just exist as an amorphous mass: they are differentiated into many different types of cell, and they are organized into recognizable, discrete structures: tissues and organs. This is accomplished by a coordinated sequen]]>