science biology revision

Cell Differentiation and Stem Cells

Stem cells are found in plants and animals. They are unspecialised or undifferentiated (meaning they have the potential to become almost any type of cell).  Once the cell is fully specialised, it will possess sub-cellular organelles specific to the function of that cell. Embryonic stem cells are more flexible in terms of what they can become compared to stem cells found in the bone marrow of adults.

Plant cells retain their ability to differentiate (specialise) throughout their life, whereas Animal cells are mainly restricted to repair and replacement in later life.

Stem cells can be used to treat humans. Therapeutic cloning can be used to treat diabetes. Embryonic stem cells (that can specialise in any type of cell) are produced with the same genes as the person who needs the treatment, when these cells are put into the body they are not usually rejected.

The benefits of using stem cells

Stem cells left over from IVF treatment (that would otherwise be destroyed) can be used to treat serious conditions.

Stem cells are useful in studying how cell division goes wrong (such as cancers).

Stem cells could be used to grow new organs for transplantation in the future.

The risks and objections of using stem cells

There is a risk of transferring viral infections by using stem cells.

Stem cells might act as a reservoir of cancer cells and spread to other parts of the body when used in an operation.

Some people believe that an embryo of any age is a human being and so should not be used to grow cells or be experimented on.

Using stem cells in plants

Plants have regions of rapid cell division called meristems.These growth regions contain stem cells that can be used to produce clones cheaply and quickly. Meristems can be used for producing large numbers of disease resistant crops and for growing and preserving rare varieties to protect them from extinction.

This video explains stem cells and how they can be used in organ transplant.

Cell division and cell enlargement is used by multicellular organisms to grow and reproduce. Plants can also grow via differentiation into branches, leaves, etc.

From the moment of fertilisation cell division begins, when the zygote replicates itself exactly through mitosis. Later in its life cycle an organism may use cell division to produce sex cells (gametes) in a different type of division called meiosis.

The stages of cell division make up the cell cycle of an organism.

Chromosomes

Chromosomes are found in the nucleus of eukaryotic cells. Chromosomes exist as pairs called homologues and are made of DNA and carry a large number of genes.

For the exact duplication of cells is it essential that all of the genetic material is duplicated. Chromosomes form a key part of a sequence of events that ensures the genetic code is transmitted exactly and appears in the new daughter cells.

DNA replication

DNA replication occurs during the cell cycle; the genetic…