Differentiation

Higher Human Biology

Differentiation

• unspecialised cells become altered and adapted

• perform a specialised function• permanent tissue• Division of labour • Multicellular organisms

Differentiation in Human Cells

• Fertilised egg (zygote)• Divides rapidly by

mitosis and cell division to form an embryo

• Many different specialised cells created – each adapted to suit its function.

• Each embryonic cell contains all the genes for constructing the whole organism

• Unlike adult cells these genes are either switched on/ have the potential to be switched on.

• As embryological development proceeds embryonic cells become differentiated and specialised in;– Structure– Biochemical properties

• Perfectly adapted to carry out particular functions.

Somatic cells

B Lymphocyte

Hyaline cartilage

Smooth muscle

Somatic cells

Ciliated epithelial cell

Red blood cellplatelets

neutrophil

Somatic cells

Cardiac muscle

Nerve cells

Squamous epithelial cells

T lymphocyte

Selective Gene Expression

• Differentiated cells only express the genes that code for the proteins specific to the workings of that particular cell.

Nerve cells - genes that code for formation of neurotransmitter substances switched on - genes for production of mucus switched off.

Goblet cells – genes that code for mucus production switched on- Genes that code for neurotransmitters switched off.

• Only a fraction of genes in a specialised cell are expressed.

• Approx 3 – 5 % in a typical human cell.