the cell cycle Flashcards
(28 cards)
state what the cell cycle is and outline its stages
● cycle of division with intermediate growth periods
● interphase
● mitosis or meiosis
● cytokinesis
explain why cell cycle does not occur in some cells
● after differentiation, some types of cell in multicellular organisations
● no longer have the ability to divide
what is the difference between the cell cycle and mitosis?
cell cycle includes growth period between divisions
outline what happens during interphase?
● G1: cell synthesises protein for replication and cell size double
● S: DNA replicates - chromosomes consist of 2 chromatids joined at a centromere
● G1: organelles divide
state the purpose of mitosis
● produces 2 genetically identical daughter cells
● growth
● cell replacement / tissue repair
● asexual reproduction
what are the stages of mitosis?
● prophase
● metaphase
● anaphase
● telophase
outline what happens during prophase
● chromosomes condense, becoming visible
(x-shaped: 2 sister chromatids joined centromere)
● centrioles move to opposite poles of cell
● nuclear membrane breaks down - chromosomes free in cytoplasm
● randomly arranged as spindle fibres not attached / formed yet
outline what happens during metaphase
● Meet in middle
● sister chromatids line at up at cell equator
● spindle fibres attach to centromere
outline what happens during anaphase
● spindle fibres contract - pulling sister chromatids to opposite poles of the cell
● chromosomes split / divide
● spindle fibres break down
outline what happens during telophase
● chromosome uncoil into DNA strands
● nuclear envelope reforms around each set of chromosomes
outline what happens during cytokinesis
cell cytoplasm and cell membrane splits
explain the procedure for a root tip squash experiment
● prepare a temporary mound of root tissue
● focus optical microscope on slide
● count total number of cells in the field of view and number of cells in a stage of mitosis
● calculate mitotic index
explain how to prepare a temporary root tip mount (5)
● place root in hydrochloric aid to stop cell division and hydrolyse cell wall
● stain root tip with dye that binds to chromosomes
● macerate tissue using mounted needle
● use mounted needle to press down coverslip and obtain a single layer of cells (to allow light through)
● avoid trapping air bubbles
what is the dye that binds to chromosome
toluidine blue
why is only root tip used when calculating a mitotic index
● cells are actively undergoing mitosis
● you can see stages of mitosis here
what are proto-oncogenes?
● stimulates cell cycle
● if mutated: cell cycle continuously active
what are tumour suppressor genes?
● produces proteins that suppress the cell cycle
● if mutated: cell cycle cannot ‘brake’
suggest how cancer treatments control rate of cell division
● disrupt the cell cycle:
● prevent DNA replication
● prevent spindle formation - inhibit metaphase / anaphase
what is cancer?
● uncontrolled cell division
● from mutation in gene that controls cell division
what is a tumour?
an abnormal group of cells
outline some features of a cancer cell
● may have more than 1 nucleus
● have different antigens on their surface
● divide faster
● have irregular shape
what are the two types of tumours?
● malignant
● benign
what is metastasis?
the migration of cancer
outline the process of semi conservative DNA replication (5)
● DNA helicase breaks hydrogen bonds between base pairs
● each strand acts as a template
● free nucleotides attach by complimentary base pairing
● DNA polymerase catalyses condensation reactions that join nucleotides on new strand with phosphodiester bonds
● hydrogen bonds reform
