B2 - Cell Division Flashcards
What is mitosis?
Occurs all around the body to produce genetically identical body cells.
What is meiosis?
Occurs in the testes or ovaries to produce gametes only.
Why does sexual reproduction produce variation?
It produces genetic variation because when the gametes fuse together one pair of chromosomes comes from each parent.
What are the male and female reproductive organs?
Testes
Ovaries
Describe the process of mitosis.
Mitosis is the division where the body creates genetically identical new cells for growth and repair.
During mitosis a copy of the chromosomes are made as the cell membrane disappears and the chromosomes move to the edge of the cell and the cell splits. Two identical daufhter cells are produced.
Describe meiosis.
Meiosis is where the cell divides to form gametes. It happens in the testes and the ovaries. The parent cell has diploid chromosomes. The DNA replicates. The cell splits off into 2 daughter cells which are not genetically identical. These cells divide again to form 4 different gametes.
The 4 daughter cells have 23 chromosomes each. When they fuse at fertilisation a full set of 46 chromosomes are made.
What happens at fertilisation?
23 chromosomes from the sperm and 23 chromosomes from the egg fuse together to become a zygote which has 46 chromosomes.
What is a stem cell?
An undifferentiated, unspecialised cell which has the potential to become a variety of cell types.
What does differentiated mean?
Some genes have been switched on and some switched off so it can only be one type of cell.
Where can adult stem cells be found?
Inside bone marrow. They can turn into red blood cells.
Where are embryonic stem cells found? Why are they so useful?
As part of an embyro. They have the potential to turn into any type of cell (muscle cells, nerve cells, epithelial cells…) They can be used as a treatment for spinal cord injuries, Parkinson’s Disease or to make new organs entirely.
Outline some ethical and social arguments for and against the use of stem cells.
Ethical
It is killing humans in some people’s view.
We have no right to play god (religious views)
Social
It can save lives
It can cure diseases
It can save money on treating the disease by other means.
What is a genetic disease?
It is inherited from parents, passed on through the gametes.
What is an infectious disease?
Passed on from one infected person to another - caused by pathogens.
Descibe polydactyly
It causes the formation of extra fingers and toes.
It is a dominant allele - only 1 parent needs to have it.
You cannot be a carrier of the disease (you would already have it as it is a dominant allele)
