Cellular differentiation and structure of the genome

Explain the meaning of cellular differentiation

Cellular differentiation is the process by which a cell expresses certain genes to produce proteins characteristic for that type of cell. This allows the cell to carry out specialised functions.

State the function of a meristem

Meristems are where cellular differentiation takes place in plants.

Meristems are regions of unspecialised cells that can divide and self-renew.

State the 2 types of stem cells and the function of stem cells in animals

The two types of stem cells are:

• Embryonic stem cells.

• Tissue (adult) stem cells.

Stem cells are unspecialised cells in animals that can divide (or self-renew) and/or differentiate.

Describe an embryonic stem cell using the term ‘pluripotent’

Cells in an early embryo can differentiate into all cell types that make up the organism.

All the genes in an embryonic stem cell can be switched on so these types of cells can differentiate into any cell types. Embryonic stems are therefore pluripotent as they can differentiate into ANY cell type.

Describe a tissue stem cell

Tissue stem cells are involved in the growth, repair and renewal of cells found in a particular tissue

Explain the term ‘multipotent’ in relation to tissue stem cells

Tissue stem cells are multipotent as they can differentiate into all the types of cell found in a particular tissue type.

E.g. Blood stem cells located in the bone marrow can only differentiate into all the types of blood cells.

Describe how stem cells are used therapeutically and in research

The therapeutic uses of stem cells involve the repair of damaged or diseased organs or tissues. Under the right conditions, in the laboratory, embryonic stem cells can self-renew.

Examples are the use in corneal repair and the regeneration of damaged skin.

Stem cells are used as model cells to study how diseases develop or being used in drug testing.

Describe ethical issues associated with using embryonic stem cells

Use of embryonic stem cells can offer effective treatments for disease and injury; however, it involves the destruction of embryos.

State what the genome is and how it is made up

The genome of the organism is its entire hereditary information encoded in DNA.

The genome is made up of genes and other DNA sequences that do not code for proteins.

Most of the eukaryotic genome consists of non-coding regions.

Describe a gene and the function of the non-coding regions

Genes are DNA sequences that code for proteins

Other sequences regulate transcription (example start and stop sequences) whilst others are transcribed but not translated.

Examples are rRNA and tRNA.