B2 Cell Division Revision

Adult stem cells

stem cells that are found in adults that can differentiate and form a limited number of cells

Cell cycle

the three-stage process of cell division in a body cell that involves mitosis and results in the formation of two identical daughter cells

embryonic stem cells

stem cells from an early embryo that can differentiate to form any specialised cells of the body

Give a disadvantage of meristem

• cloned plants are genetically identical, so a whole crop is at risk of being destroyed by a single disease or genetic defect

Give three advantages of adult stem cells

• fewer ethical issues; adults can consent to have their stem cells removed and used

• it's an already established technique for treating diseases such as leukaemia

• relatively safe to use as a treatment and donors recover quickly

Give three advantages of embryonic stem cells

• can treat a wide range of diseases as they can form any specialised cell

• may be possible to grow whole replacement organs

• usually no donor needed as they are obtained from spare embryos from fertility clinics

Give three advantages of meristem

• rare species of plants can be cloned to prevent extinction

• plants with desirable traits, such as disease resistance, can be cloned to produce large numbers of identical plants

• fast & low-cost production of large numbers of plants

Give three disadvantages of adult stem cells

• requires a donor, potentially meaning a long wait time to find someone suitable

• can only differentiate into certain types of specialised cells, so can be used to treat fewer diseases

• relatively safe to use as treatment and donors recover quickly

Give three disadvantages of embryonic stem cells

• ethical issues arise as the embryo is potential life

• risk of transferring viral infections to the patient

• newer treatment so relatively under-researched, efficacy not fully confirmed

therapeutic cloning

a process where an embryo is produced that is genetically identical to the patient so the cells can then be used in medical treatments

Plant meristems

area where rapid cell division occurs in the tips of roots and shoots

Three stages of the cell cycle

1 - Interphase (cell growth and DNA replication) 2 - Mitosis (nuclear division) 3 - Cytokinesis (cytoplasm divides to form two identical cells)

Stage 2 of the cell cycle - mitosis

A complete set of chromosomes is pulled to each end of the cell and the nucleus divides to form two nuclei

First stage of the cell cycle

Cells grow bigger; (DNA) chromosomes duplicate; number of sub-cellular structures (e.g. ribosomes and mitochondria) increases

Stage three of the cell cycle

cytoplasm and cell membrane divide to form two identical daughter cells

Where are adult stem cells found?

bone marrow

Where are embryonic stem cells found?

early human embryos (usually from spare/aborted embryos from fertility clinics)

Where is meristem found?

The roots and shoots of plants

Why is there some concern around using embryonic stem cells?

They divide and grow rapidly which is ideal for cancer to form in

Type of cells that undergo cell division

Eukaryotic