Cell divison Flashcards
why is cell division important
- for an organism to grow
- for repair of damaged or dead tissue
- for the replacement of dead or damaged cells
what are diploid cells
cells with two matching sets of chromosomes in the nucleus
what are haploid cells
cells with only one set of chromosomes
example of a haploid cell
sperm and egg cells
example of diploid cells
all other cells apart from sperm and egg cells
what happens to the chromosomes during mitosis
the cells replicate prior to mitosis
why do the cells replicate before mitosis
so the daughter cells produced have exactly the same number of chromosomes as the parent cell
this is important so there is no loss of genetic info in the daughter cell
what are chromosomes made of
each chromosomes are made up from two identical chromatids joined at the centromere
what happens in stage one of mitosis
dna in the nucleus coils into single stranded chromosomes (visible in the nucleus )
what happens in stage two of mitosis
the single stranded chromosomes replicate in preparation for cell division
what happens in stage three of mitosis
chromosomes ( pairs of chromotids ) line up along the equator of the cell
what happens in stage four of mitosis
spindle fibre form, attaching to the centromere. As these contract they pull the chromotids apart towards opposite ends of the cell
what happens in stage five of mitosis
nuclear membrane reforms around both sets of chromosomes
what happens in stage six of mitosis
cytoplasm splits producing two identical daughter cells
what does the specialisation of cells lead to
the formation of a variety of cells, tissues and organs
what do organs do
organs perform different functions, and the cells in organs are specialised for their function
state the hierarchy of the body
cells — tissues — organs — systems
describe stem cells in animals
unspecialised cells which can divide in order to self renew
they also have the potential to differentiate to become specialised cells (diffrent types of cells with a specific function)
what are stem cells used for in animals
growth and repair
what are the two types of stem cells
Embryonic stem cells
tissue stem cells
what are embryonic stem cells
cells that can be obtained from the embryo at a very early stage
what are tissue stem cells and examples
cells which can be found in the body throughout life
for example skin, bone marrow and brain
