B2: Cell Division Flashcards
What do chromosomes do?
They carry genes that contain the instructions for making new cells.
Genes contain information for a particular characteristic and is a section of DNA.
What is the importance of mitosis?
It produces additional cells needed for growth and repair in organisms and for the replacement of worn out/damaged cells. They are important in growth, repair and development of multicellular organisms.
What are the 3 stages of the cell cycle?
- Interphase - The cell grows in size. DNA and sub-cellular organelles replicate to form two copies of each chromosome for cell division. Number of mitochondria, ribosomes and chloroplasts increases and protein synthesis occurs.
- Mitosis - Replicated chromosomes line up at the centre of the cell. Spindle fibres contract and chromosomes are pulled to opposite poles. Nucleus divides.
- Cytokinesis - Cell membrane and cytoplasm divide to form 2 genetically identical daughter cells.
What are stem cells?
Stem cells are unspecialised cells that have the ability to differentiate into any other type of cell.
What are the features of stem cells in animal and plant cells?
Most plant cells are able to differentiate throughout their entire lives. Stem cells are found in the meristems - roots and shoots.
Animal cells mostly differentiate at the early stages of their development. Stem cells can be found in embryos or bone marrow.
What is growth?
The process of cell division followed by the cells becoming specialised.
What are embryonic stem cells?
• They form when an egg and sperm cell fuse to form a zygote.
- Can differentiate into any type of cell in the body.
- Can be cloned or directed to differentiate into any cell.
- Can be used to treat diabetes (insulin producing cells), paralysis (nerve cells) and heart problems, blindness etc.
What are adult stem cells?
- Stem cells found in adult tissues such as bone marrow, brain and muscles.
- Can only differentiate into cells from the type of tissue they are formed.
What are the advantages and disadvantages of adult stem cells?
Advantages: Plentiful supply, No ethical issues as consent can be given, Safer method as it is well tested/tried.
Disadvantages: Painful to extract, fewer diseases can be treated as they only form cells from a particular tissue, possibility of infection during extraction.
What are the advantages and disadvantages of embryonic stem cells?
Advantages: Have potential to develop into any cell, more diseases can be treated, painless.
Disadvantages: Unethical, possible harm/death to the embryo, expensive, less reliable.
What is the importance of both adult and embryonic stem cells?
Both can be used to replace damaged/diseased body parts, can improve research into differentiation.
What is therapeutic cloning?
It involves an embryo being produced with the same genes as the patient.
- Nucleus from human skin cell is removed and kept. Nucleus from human egg cell is removed. Skin cell nucleus is inserted into the empty egg cell. The egg cell is given an electric shock to stop it dividing and it develops into an embryo with stem cells.
