B2 Cell division

What do we find in the nucleus , something that is made out of the molecule DNA

chromosomes

What is the difference between gametes and normal cells

Gametes have chromosomes which are not paired —>½ number of chromosomes

what do chromosomes do

Carry a large number of genes determining many of our features

What is the cell cycle

When cells have to be able to divide (meiosis or mitosis)

Stages of mitosis

1)DNA replicates to form 2 copies of each chromosome

• The cell grows and copies its internal structures (such as mitochondria and ribosomes)

2)Mitosis takes place , one set of chromosomes is pulled to each end of the cell and the nucleus divides

3)Cytoplasm and cell membrane divideto form 2 identical cells

Why is mitosis important

• Growth and development for multicellular organisms

• Mitosis takes place when an organism repairs itself (injuries)

• Mitosis happens during asexual reproduction

How is an embryo formed and what is an embryo

A ball of cells (embryo)

Sperm + egg/ovum = fertillised egg/ovum

The fertillised egg/ovum undergoes mitosis to become an embryo

How does an embryo form specialised cell

The embryo undergoes mitosis and change and begin to form specialised cells

Have cells in the early embryo differentiated

no - Any of those cells in embryo are capable of differentiating into any type of cell

What is a stem cell

Undifferentiated cell which can give rise to more cells of the same type and can differentiate to form other types of cells

Where can we find adult stem cells

Bone marrow —> CAN ONLY DIFFERNTIATE INTO CELLS FOUND IN OUR BLOOD (RBC , WBC , PLATLETS)

Difference between adult and embryonic stem cells

• Adult stems cells can only differentiate into cells found in our blood

• Embryonic stem cells can differentiate into any cell

process of bone marrow transplant

• Leukaemia is a cancer of bone marrow , to treat this we :

1)Destroy the patients existing bone marrow using radiation

2)The patient receives a transplant of bone marrow from a donor

3)The stem cells in the bone marrow now divide and form new bone marrow and differentiate and form blood cells

What are the 2 problems with bone marrow transplants

1)The donor has to be compatible with the patient otherwise the WBCs produced by the donated bone marrow could attack the patients body

2) There is a risk viruses can be passed from the donor to the patient

What is another way of using stem cells in medicine

Therapeutic cloning

What happens in therapeutic cloning

1)An embryo is produced with the same genes as the patient

2)Stem cells from the embryo can be transplanted into the patient without being rejected by the patients immune system

3)Once inside the patient , the stem cells differentiate to replace cells which have stopped working properly

Examples of what therapuetic cloning is useful for

• Diabetes

• Paralysis

Any concerns with therapeutic cloning

Religious/ethical objections

Examples of stem cells in plants

Meristem tissue

What does meristem tissue do

These stem cells can differentiate into any plant tissue at any point in the plants life

Uses of meristem tissue

• Clone a rare plant to stop it from going extinct

• Produce cloned crop plants for farmers