Cell division Flashcards
what is the cell cycle
a highly ordered sequence of events that takes place in a cell
what does the cell cycle result in
division of the cell and the formation of two genetically identical daughter cells
what are the two main phases of the cell cycle
interphase and mitotic (division) phase
why do we need new cells
for growth and repair
whats a period of cell division called
M phase
what does M phase involve
mitosis and cytokinesis
what are the three separate growth stages of interphase
G1, s, G2
what happens during interphase
- the cells prepare to divide
- the cell’s DNA is unravelled and replicated
- the organelles are also replicated so it has spare ones and its ATP content is increased
what is mitosis needed for
growth an repair
what kind of process is mitosis
continuous process but is described as a series of stages
what is the chromosomes structure
the chromsomes are made of two strands joined in the middle by a centromere
the separate strands are called chromatids
two strands on the same chromosome are called sister chromatids
why is there two strands of chromosomes
each chromosome has already made an identical copy of itself during interphase
what happens to the chromosome when mitosis is over
the chromatids end up as one-strand chromosomes in the new daughter cells
what happens during prophase
the chromosomes condense
centrioles move to the opposite ends of the ceell, forming protein fibres across called the spindle
- the nuclear envelope breaks down and chromosomes lie free in the cytoplasm
what happens during metaphase
the chromosomes line up along the middle of the cell and become attache to the spindle by their centromere
- at the metaphase checkpoint, the cell checks all the chromosomes are attached to the spindle before mitosis can continue
what happens during anaphase
the centromeres divide, separating each pair of sister chromatids
- the spindles contract, pulling chromatids to opposite ends of the cell, centromere first
what happens during telophase
the chromatids reahc opposite poles on the spindle
they uncoil and become long and thin again
they are now called chromosomes again
a nuclear envelope forms arounf each group of chromosomes
what happens during cytokinesis
the cytoplasm divides
a cleavage furrow forms to divide the cells
two genetically identical daughter cells are formed
when does cytokinesis begin
in anaphase
when does cytokinesis end
telophase
how do investigate mitosis
to do this you treat the tips of the growing roots in HCl and break them open carefully and spread a few on a microscopic slide
- add a few drops of stain
- squash under a coverslip
- view under microscope
what are gametes
sperm cells and egg cells
what happens during sexual reproduction
two gametes join together at fertilisation to form a zygote
what number of chromosomes do gametes have?
a haploid numberw
how many chromsomes does a body cell have?
a diploid number
what is meiosis
cell division that produce gametes
are gametes genetically identical?
no they are genetically different because each cells ends up with a combination of chromosomes
what is the first phase of meiosis
interphasein
what happens during interphase of meiosis
the cells DNA unravels and replicates to produce double-armed chromosomes (sister chromatids)
what is meiosis 1
involves two divisions (M1 and M2)
after interphase the cell enter M1
M1 is the reduction division (it halves the chromosome number)
