Studied by 3 people
The cell cycle
Cells divide in a series of stages. Te genetic material is doubles and divided into two identical cells.
What does a cel have t do before it can divide? (interphase/growth phase)
It needs to grow and ncrease the number of sub-cellular structures such as ribosome and mitochondria
the DNA replicates to form two copies of each chromosome
What happens in mitosis?
one set of each chromosome is pulled to each end of the cell and the nucleus divides
What happens in the last stage of cell cycle? (cytokinesis)
The cytoplasm and cell membrane divides to form two identical cells
reasons why mitosis is important
for growth and development of multi cellular organisms
for repair of damaged cells
what is a stem cell?
A stem cell is an undifferentiated cell of an organism which is capable of giving rise to mny more cells of th same type, and from which certain other cells can arise from differentiation.
How to calculate the length of time in different stages.
lenth of time in stage= (observed number of cells in stage/ total numbers of cells observed) x total time of cell cycle
Benefits of therapeutic cloning in plants
Rare species can be cloned to protect from extinction
crop plants with special features such as disease resistance can be cloned to produce large numbers of identical plants for farmers
crops with resistance to pest can be cloned
Why is theraputic cloning/ the method of peroducing stem cells opposed by many people?
The embryo may die in the process
if implanted, the embroyo would develop into a clone of the patient
religious/moral/ethical beliefs
Disadvantage of using stem cells from meristem in plants
there will be low genetic diversity in the cloned plants
Difference between embryonic stem cell differs from adult stem cells
Embroyonic stem cells have not differentiated and can differentiate into most types of human cells
adult stem cells can form many but not all types of cells (e.g. blood cells)
Embryonic stem cells are only found in embryos / early is develoment
Adult stem cells are present in humans regardless of age
The pros of embrtnic stem cells
can be used to treat a wide variety of diseases
Embryonic stem cells are sourced from embryos made in IVF and more are usually made than are used
The potential benefits of being able to treat more conditions and diseases with embryonic stem cells (to prevent human suffering) outweighs the consequences, especially as many embryos produced during IVF treatment are just discarded without having a use
Disadvantages of using stem cells
The long-term effects of embryonic stem cells are not known
Using embryos as a source of embryonic stem cells is controversial as some consider the practice to cause harm to an embryo which cannot give consent
Disadvantages of adult stem cells
they can only differentiate into fewer types of specialised cells and may only be useful in treating a smaller number of disease
very painful operation
there are hazards if an operation to consider
Advantages of adult stem cells
no ethical issues to consider if an adult consents to donating their bone marrow
has been used as a source of stem cells for treatment for much longer and is more tried and tested (and therefore reliable);
Outlined process by which a cell divides by mitosis
After the chromosomes are duplicated
the chromosomes separate
cytokynesis occurs (the cell membrane and cytoplasm divides)
two genetically identical daughter cells are formed
Why can you use therapeutic cloning to treat disease but not to produce a baby
Any baby produced in this way would be a clone as the genetic material only came from one individual which is illegal
Cloning has many ethical issues; is a clone the property of the person it was cloned from or its own individual with its own rights?
The cells would be used to treat disease and not used to make a baby
Many different types of cells could be produced and used for research to help treat many diseases
Any cells produced would have the same genetic makeup as the patient
so there would be no issues of tissue rejection
How can embryonic stem cells treat paralysis
Paralysis is caused by damage to neurones in the spinal cord (which cannot be repaired);
Embryonic stem cells are unspecialised and could be manipulated to differentiate into neurones / nerve cells / their supporting cells;
Which could be used to replace the cells damaged in the spine;
How does a foetus form through mitosis from a zygote ?
Mitosis increases the number of cells
cell differentiation occurs
to create speacialise dcells which carry out particular fuctions
How can embryonic cells be used to treat a heart attack when the coronary artery becomes blocked .
Stem cells can be removed from an ealy embryo.
Could be stimulated to develop into heart muscle tissue
these stam cells could then be transferred/implanted int the patient
to repair the damaged tissues/cells
