B3 Cell Division Flashcards
What is a stem cell?
A stem cell is an undifferentiated cell that can differentiate into one or more specialised cell types
What are adult stem cells?
Stem cells from adult bone marrow that can only differentiate into certain specialises cells
What are embryonic stem cells?
Stem cells from early embryos that can differentiate into any specialised cell
What is therapeutic cloning?
It is when the patient’s cells are used to create an early embryo clone of themselves- stem cells from the embryo can then be used to treat the patient’s medical condition
Give an advantage of therapeutic cloning
The stem cells from the embryo are not rejected when transplanted because they have the same genes as the patient
Give an advantage of using adult stem cells
There are fewer ethical issues because the adults can consent to their use
Give two disadvantages of using adult stem cells
It can take a long time for a suitable donor to be found
Can only differentiate into some specialised cell types, so it can only treat fewer diseases
Give two advantages of using embryonic stem cells
Can differentiate into any specialised cell
Easier to obtain as they are found in spare embryos from fertility clinics
Give two disadvantages of using embryonic stem cells
Ethical issues surrounding their use, as every embryo is a potential life
Potential risks involved with treatments, such as transfer of viral infections
What are plant meristems?
An area where rapid cell division occurs in the tips of roots and shoots
Give two advantages of using plant meristems to clone plants
Rare species can be cloned to prevent extinction
Plants with special features such as disease resistance can be cloned to produce many copies of
Give one disadvantage of using plant meristems to clone plants
No genetic variation, so for example an entire cloned crop could be destroyed by a disease
What is cell division by mitosis?
When the body cells divide to form two identical daughter cells
What is the purpose of mitosis?
For the growth and repair of cells, asexual reproduction
What happens during the first stage of the cell cycle?
The cell grows bigger, chromosomes duplicate, number of sub cellular for example ribosomes and mitochondria increases
What happens during mitosis?
One set of chromosomes is pulled to each end of the cell and the nucleus divides
What happens during the third stage of the cell cycle?
The cytoplasm and cell membrane divide, forming two identical daughter cells
What happens during the second stage of the cell cycle?
A complete set of chromosomes is pulled to each end of the cell
The nucleus divides to form two nuclei
What is variation?
Variation is the presence of differences between living things
Where does variation occur?
Variation occurs between organisms of the same species(like humans) and also between different species
What is environmental variation?
A variation due to the environment
Provide examples of environmental variation
Scars
Tattoos
A sun tan
Define gene
A length of DNA that codes for a protein
Examples of genes?
Hair colour
Eye colour
