T2: The Cell Cycle and Mitosis Flashcards
what is the cell cycle?
interphase
nuclear division (mitosis)
cell division (cytokinesis)
what is mitosis?
the part of the cell cycle in which a eukaryotic cell divides to produce two genetically identical daughter cells
what are the stages of mitosis?
PMAT
Interphase before
Cytokinesis after
why is mitosis needed?
produces 2 genetically identical cells for growth and repair
describe interphase
cell prepares to divide: energy stores increase + cell gets bigger
organelles are replicated
DNA is unravelled and copied
describe prophase
chromosomes condense and are now visible when stained
the chromosomes consist of two sister chromatids joined together at the centromere
the two centrosomes move towards opposite poles
spindle fibres begin to emerge from the centrosomes
the nuclear envelope breaks down into small vesicles
describe metaphase
each centrosome reaches a opposite pole
chromosomes line up across the equator of the spindle, attached by their centromeres
describe anaphase
centromeres divide separating each pair of sister chromatids
spindle fibres begin to shorten pulling sister chromatids to opposite ends of the cell
describe telophase
chromatids reach opposite poles and uncoil
spindle fibres break down and a nuclear membrane forms around DNA
how many chromosomes do human diploid cells have?
46 chromosomes
before the parent cell undergoes mitosis there is 92 in the nucleus
what can be seen during prophase?
chromosomes are visible
nuclear membrane is breaking down
what can be seen during metaphase?
chromosomes are lined up along the middle of the cell
what can be seen during anaphase?
chromosomes are moving away from the middle of the cell, towards opposite poles
what can be seen during telophase?
chromosomes have arrived at opposite poles of the cell
chromosomes begin to decondense
the nuclear envelope is reforming
2 groups of chromosomes (one at each pole)
why do you place root tips in ethanol?
helps to “fix” the tissue and prevent mitosis from continuing in the cells
why do you place root tips in warm HCl?
separates the cells
why do you press down on the coverslip after adding it to a specimen on a slide?
spreads out the cells so they are all one layer thick
how to calculate mitotic index?
mitotic index = number of cells with visible chromosomes ÷ total number of cells
what causes cancer?
uncontrollable cell division
cancers start when mutations occur in the genes that control cell division
most mutations either result in early cell death or result in the cell being destroyed by the immune system
cancerous cells do not die so can be passed on
what are benign tumours?
tumours that do not spread from their original site
do not cause cancer
what are malignant tumours and why is it difficult to treat them?
malignant tumours spread through the body
+ interfere with the normal functioning of the organ / tissue
their cells can break off and travel through the blood to form secondary growths
it can be difficult to detect, locate and remove secondary cancers
what are plasmids?
smaller, circular DNA molecules that are also replicated and inherited
the number of copies of plasmids that each cell inherits can vary
describe binary fission in prokaryotes
the single, circular DNA molecule undergoes DNA replication
any plasmids present undergo DNA replication
the parent cell divides into two cells, with the cytoplasm roughly halved between two daughter cells
the two daughter cells each contain a single copy of the circular DNA molecule and a variable number of plasmids
describe the appearance of chromosomes during prophase
chromosomes become visible and appear as two sister chromatids joined at the centromere
describe the appearance of chromosomes during metaphase
chromosomes line up on the equator of the cell
they are attached to spindle fibres by their centromeres
describe the appearance of chromosomes during anaphase
the centromere splits
sister chromatids are pulled to opposite ends of the cell
describe the appearance of chromosomes during telophase
chromatids unwind becoming longer
