B2 Cell division Flashcards
What does the nucleus contain?
genetic material in the form of chromasomes
What is the cell cycle?
When body cells divide to produce new cells
What do chromosomes contain?
genes to control the development of different characteristics
What are chromosomes?
coiled up lengths of DNA molecules
How many chromosomes do humans have?
23 PAIRS (46 single)
(one from the mother and one from the father)
what is mitosis?
where a cell reproduces by splitting in to two identical cells
What is mitosis used for in multicellular organisms?
to grow and replace damaged cells
what are the stages of the cell cycle?
- Number of subcellular structures increases. Chromosomes duplicate
- chromosomes line up and cell fibres pull the two arms of the chromosomes to opposite ends. Membranes form around the chromosomes which become nuclei
- cytoplasm and membranes divide. two daughter cells are produced
What is differentiation?
the process where a cell changes to become specialised for it’s job
What does differentiation allow cells to do?
to carry out specific functions as they have different subcellular structures
when does most differentiation occur?
as an organism develops
- in animal cells, the ability to differentiate is lost early
- plant cells do not lose the ability
What are the cells that differentiate in mature animals used for?
repairing and replacing cells
what are stem cells?
undifferentiated cells
where do stem cells come from?
- early human embryos
- adult bone marrow
What can embryonic stem cells do that adult stem cells can’t?
embryonic stem cells can differentiate into any cell
what are adult stem cells already used for?
to cure diseases
eg. replacing faulty blood cells
what can embryonic stem cells be used for?
to replace faulty cells
eg. insulin producing cells, nerve cells
what is therapeutic cloning?
where an embryo is made to have the same genetic information as the patient.
this means the stem cells would not be rejected by the patient
What are the risks of stem cells?
They could be infected with viruses and this could transfer to the patient.
adult stem cells could be rejected by the patient.
how do bacterial cells divide?
simple cell division where 1 cell splits into 2 bacterial cells. this is known as binary fission.
what is the formula to calculate the number of bacteria?
number of bacteria = 2n (number of rounds of division)
name some aseptic techniques:
sterilising by passing the aperatus through a flame
sealing the petri dish with tape to stop unwanted microorganisms contaminating
clean surfaces with disinfectant
why are bacteria grown at 25 degrees in school labs?
to reduce the chance of harmful bacteria growing
why are the petri dishes stored upside down?
to prevent condensation dripping into the samples
how can you measure the efficacy of an antibiotic on an agar plate?
calculate the area of the zone of inhibition (where bacteria have not grown)
where are stem cells found in plants?
in meristem tissue
when can stem cells in plants differentiate?
at any point in the life of the plant
what are the uses of plant stem cells?
a rare plant can be cloned to stop it going extinct
crop plants can be cloned
