cell division + cancer Flashcards
what does mitosis produce
a parent cel divides to produce two genetically identical daughter cells
why is mitosis needed
for growth of multicellular organisms and for repairing damaged tissues
cell cycle
G1 - cell grows and new organelles and proteins are made
synthesis - cell replicates its DNA, ready to divide by mitosis
G2 - cell keeps growing and proteins needed for cell division are made
Mitosis
interphase - cell growth and DNA replication
Order of mitosis stages
Interphase Prophase Metaphase Anaphase Telophase
Interphase
the cell carries out normal functions, but also prepares to divide
The cell’s DNA is unravelled and replicated, to double it’s genetic content
The organelles are also replicated so it has spare ones, and its ATP content is increased
Prophase
the chromosomes condense, getting shorter and fatter
tiny bundles of protein called centrioles start moving to opposite poles of the cell, forming a network of protein fibres across it call the spindle
the nuclear envelope breaks down and chromosomes lie free in the cytoplasm
metaphase
the chromosomes line up along the middle of the cell and become attached to the spindle by their centromere
anaphase
the centromeres divide, separating each pair of sister chromatids
the spindles contract, pulling chromatids to opposite poles of the spindle, centromere first
This makes the chromatids appear v-shaped
telophase
the chromatids reach the opposite poles on the spindle
they uncoil and become long and thin again
they’re called chromosomes again
a nuclear envelope forms around each group of chromosomes, there are now two nuclei
division of the cytoplasm (cytokinesis which starts in anaphase) finishes in telophase
there are now two daughter cells that are genetically identical to the original cell and to eachother
time taken calculation
10 out of 100 cells take 15 hours in metaphase
10/100 x (15x60) = 90 mins in metaphase
what is cancer the result of
uncontrolled cell division
mitosis and the cell cycle are controlled by genes
normally, when cells have divided enough times to make enough new cells, they stop - but it there’s a mutation in a gene that controls cell division, the cells can grow out of control
the cells keep on dividing to make more and more cells which form a tumour
cancer is a tumour that invades surrounding tissues
what do treatments of cancer do
control the rate of cell division in tumour cells by disrupting the cell cycle
disrupting G1
preventing the synthesis of enzymes needed for DNA replication - if these aren’t produced, the cell is unable to enter the synthesis phase, disrupting the cell cycle and forcing the cell to kill itself
disrupting synethsis
damage DNA
at several points in the cell cycle (including just before and during S phase) the DNA in the cell is checked for damage
If severe damage is detected, the cell will kill itself - preventing further tumour growth
formula for actual size
actual size = size of image/magnification
