mitosis Flashcards
cell cycle
the regulated sequence of events that occurs between cell divisions
3 phases of the cell cycle:
interphase
nuclear division (mitosis)
cell division (cytokinesis)
what happens during interphase?
the cell increases in mass and size and carries out its normal cellular functions
3 phases of interphase:
G1 phase
S phase
G2 phase
what happens in the G1 phase?
cells make the proteins required for growth (eg: enzymes)
what happens in the S phase?
the DNA in the nucleus replicates
what happens in the G2 phase?
the cell continues to grow and the new DNA that has been synthesised is checked and any errors are usually repaired
what is mitosis?
nuclear division where two genetically identical haploid daughter cells are produced
why is mitosis useful?
-it lets unicellular zygotes grow into multicellular organisms
-damaged tissues can be repaired by mitosis
asexual reproduction
offspring are genetically identical to the single parent used to produce them
prophase
-chromosomes condense and are visible
-the two centrosomes move towards opposite poles
-spindle fibres begin to emerge from the centrosomes
-the nuclear envelope breaks down
metaphase
-centrosomes reach opposite poles
-chromosomes line up at the equator
-spindle fibres reach the chromosomes and attach to the centromeres
anaphase
-the sister chromatids separate at the centromere
-spindle fibres begin to shorten
-the chromosomes are pulled to opposite poles by the spindle fibres
telophase
-chromosomes arrive at opposite poles and begin to decondense
-nuclear envelopes reforms around each set of chromosomes
-the spindle fibres break down
cytokines
the cytoplasm divides, this results in two genetically identical cells
how do cancers start?
when changes happen in the genes that control cell division (mutation)
how is mitosis affected in cancer?
uncontrolled mitosis, which forms a tumour
what is an oncogene?
a mutated gene that causes cancer
are mutations common?
yes
do mutations usually have a negative effect?
no:
-most mutations either result in early cell death or result in the cell being destroyed by the body’s immune system
(most cells can be easily replaced, so these events usually have no harmful effect on the body)
what are carcinogens?
any agents that may cause cancer
examples of carcinogens:
-UV light
-tar in tobacco smoke
-X-rays
which tumours don’t spread from their original site?
benign (don’t cause cancer)
which tumours invade neighbouring tissue?
malignant (cause cancer)
