Cells and control I
Mitosis
Genetic information
The nucleus of cells in our body contain genetic material needed for growth and repair
Stored in DNA in chromosomes
23 chromosome pairs in each human cell
46 chromosomes in total
Body cells normall have 2 copies of each chromosome, diploid
Stages
1) Interphase - before division, the cell has to grow and increase the amount of mitochondria and ribosomes. DNA is replicated
2) Prophase - Chromosomes condense, cell membrane breaks down. The chromosomes lie free in the cytoplasm
3) Metaphase - Chromosomes line up at the centre of the cell
4) Anaphase - Chromatids seperate and the Spindle fibres pull one chromatid from each pair is pull the poles of the cell
5) Telophase- Membranes form around the chromosomes, becomes the nucleus and spindle fibres break down
6) Cytokineses: Before telophase ends, cytoplasm and the membrane divide, forming 2 new genetically identical cells
Uses
Growth
Repair
Asexual reproduction
Cell growth and differentiation
Growth in animals
A fertilised egg divides by mitosis to produce genetically identical daughter cells.
These cells grow and divide by mitosis, and eventually differentiate into different types of cells to make up a whole organism
Differentiation creates specialised cells adapted to carry out a particular function
Growth in plants
Plant cells divide by mitosis, just behind the tips of shoots and roots
After the cells grow, young cells take in water by osmosis and enlarge, causing the cells to elongate
These cells can differentiate into specialised cell types
Most plant cells continue to grow and differentiate throughout life
Cell differentiation - when a cell changes to become more specialised for it's job
Allows the organism to work more effectively
Each cell type carries out a different function
Stem cells
Cells in an embryo are unspecialised. They divide to produce all specialised cells in the body. Once the cells have differentiated they cannot divide to produce other kinds of cell
Stem cells are cells that can divide to produce many types of cell
Embryonic stem cells
Adult stem cells
Plants
Taken from embryos at a very early stage of division, can differentiate into any type of cell in the body
Replace and repair brain cells to treat people with Parkinson's disease
Replacing damaged cells in the retina of the eye to treat some kinds of blindness
Growing new tissues in the lab to use for transplants
Adult stem cells are found in differentiated tissue, such as bone or skin - they divide to replace damaged cells
From bone marrow
Can only form a limited number of cell types
Used in Leukaemia treatment
Can potentially be used in growing new tissues that are genetically matched to the patient
Produce all type of cell
Issues
Rejection - the body may recognise cells as foreign
Tumor - Stem cells may not stop dividing and lead to cancer
Disease transmission - Viruses could be passed between donors
Plants have meristems that are found in rapidly growing parts of the plant, these cells can divide to produce any kind of plant cell
Meristems produce unspecialised cells that are able to divide
Unspecialised cells go on to form tissue like xylem and phloem
Meristems are found in the root tips and shoots
Totipotent stem cells
Multipotent stem cells
Totipotent stem cells
Almost all cells differentiate at an early stage and then lost this ability
In mature aniamls, cells division only happens to repaire or preplace damage cells
Most specialised cells can make more of the same cell through mitosis
Cells like red blood cells lose their nucleus and cannot divided, so are replaced by adult stem cells
Can lead to uncontrolled cell division, which leads to a tumour
If the parent plant has certain desirable features
Therapeutic cloning
Embryo produced could then be harvested to obtain the embryonic stem cells
Can be grown to any cells that the ptaient needed
Wouldn't be rejected as they would have the exact same genetic make up as the individual
Benefits
Can replaced damaged or diseased body parts
Unwanted enbryos from fertility clinics could be used, which would otherwise be discarded