Transcript Differentiation and Stem Cells

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
Smooth muscle
Hyaline cartilage
Somatic cells
neutrophil
Ciliated epithelial cell
Red blood cell
platelets
Somatic cells
Cardiac muscle
Squamous epithelial
cells
Nerve 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.