KA 1.1 : Division and differentiation in human cells

What are somatic cells?

• Somatic cell is any cell is the body other than cells involved in reproduction

• Somatic cells are diploid, which means they have 23 pairs of homologous chromosomes

• Somatic cells divide by mitotis to form more somatic cells

What are germline cells?

• Germline cells are gametes (sperm and ova) and the stem cells that divide to form gametes

• The gamete cells are haploid and contain 23 single chromosomes

• Germline cells divide by mitosis and by meiosis

What is cellular differentiation?

• Cellular differentiation is the process by which a cell expresses certain genes to produce protein characteristics for that type of cells

• This allows a cell to carry out specialised functions

Stem cells- Cells in the very early embryo

• Cells in the very early embryo are pluripotent and can differentiate into all the cell types that make up the individual

• This can happen as all the genes in embryonic stem cells can be switched onn

Stem cells- Tissue stem cells

• Tissue stem cells are involved in the growth, repeair and renewal of the cells found in that tissue

• They are multipotent as they can differentiate into all of the types of cell found in a particular tissue

• For example blood stem cells located in bone marrow can give rise to, red blood cells, platelets, phagocytes and lymphocytes

Therapeutic uses of stem cells

• This involves the repair of damaged or diseased organs

• For example corneal repair and regeneration of damaged skin

Research uses of stem cells

• Stem cells from the embryo can self-renew under the right conditions in the lab

• Stem cell research provides information on how cell processes such as cell growth, differentiation and gene regulation work

• Research uses involve stem cells being used as, model cells to study how diseases develop and for drug testing

Cancer cells

• Cancer cells divide excessively because they do not respond to regulatory signals

• This results in a mass of abnormal cells called a tumour

• Cells within the tumour may fail to attach to each other, spreading throught the body to form a secondary tumor