2.1.6 Cell Division, Cell Diversity And Cellular Organisation Flashcards
(52 cards)
Describe the cell cycle
Interphase (G1, S, G2)
Mitotic phase (mitosis, cytokinesis)
What processes occur during G1
Proteins that synthesise organelles are produced
Organelles replicate
Cell increases in size
What processes occur during S phase
DNA is replicated in nucleus
What processes occur during G2
Cell increases in size
Energy stores increased
Duplicated DNA checked for errors
What processes occur during mitosis phase of the cell cycle
Nucleus divides
What processes occur during cytokinesis phase of the cell cycle
Cytoplasm divides and 2 cells are produced
Name the checkpoints in the cell cycle
G1 checkpoint
G2 checkpoint
Spindle assembly checkpoint
What is the G1 checkpoint for
End of G1 phase
Checks cell size, nutrients, growth factors, DNA damage
What is the G2 checkpoint for
End of G2 phase
Checks cell size, DNA replication and damage
What’s the spindle assembly checkpoint for
Checks for chromosome attachment to spindles, during mitosis
Mitosis can’t proceed until checkpoint is passed
Order of phases in mitosis
Prophase
Metaphase
Anaphase
Telophase
Describe the events in prophase in mitosis
Chromatin fibres coil and condense to form chromosomes
Nucleolus disappears
Nuclear membrane breaks down
Spindle fibres form linking poles of cell
(Centrioles go to poles of cell in animal cells and some plant cells)
Spindle fibres attach to areas on centromeres and move chromosomes to centre of cells
Describe the events in metaphase in mitosis
Chromosomes moved by spindle fibres to form plane in centre of cell (metaphase plate) and held in position
Describe the events in anaphase in mitosis
Centromeres divide
Sister chromatids separated, pulled to opposite poles of cell by shortening spindle fibres
Describe the events in telophase in mitosis
Chromatids reached the poles, chromosomes
Sets of chromosomes assemble at each pole, nuclear envelope reforms around them
Chromosomes start to uncoil, nucleolus forms
How does cytokinesis occur in animal cells in mitosis
Cleavage furrow forms around middle of cell
Cell-surface membrane pulled inwards by cytoskeleton until close enough to fuse around the middle, forms 2 cells
How does cytokinesis occur in plant cells in mitosis
Cleavage furrow can’t form due to cell walls
Vesicles from Golgi assemble in same place as metaphase plate
Vesicles fuse with eachother and cell-surface membrane, divides cell in 2
New sections of cell wall form along new sections of membrane
Why is mitosis important in life cycles
Necessary when daughter cells have to be identical: growth, replacement, repair of tissues
Necessary for asexual reproduction
What is meiosis I
Reduction division
Pairs of homologous chromosomes separated into 2 cells
Haploid cells created
What is meiosis II
Pairs of chromatids in each cell separated forming 2 cells, 4 haploid daughter cells produced
Describe the events of prophase 1 in meiosis I
Chromosomes condense, nuclear envelope breaks down, nucleolus disappears
Spindle formation begins
Homologous chromosomes pair up, form bivalents
Crossing over occurs
Describe the events of metaphase 1 in meiosis I
Homologous pairs of chromosomes assemble along metaphase plate
Independent assortment of orientation of each homologous pair results in genetic variation
Describe the events of anaphase 1 in meiosis I
Homologous chromosomes pulled to opposite poles, chromatids stay joined together
Sections of DNA on sister chromatids break off and rejoin at chiasmata, genes exchanged between chromatids
Sister chromatids no longer identical, genetic variation arises
Describe the events of telophase 1 in meiosis I
Chromosomes assemble at each pole and nuclear membrane reforms, chromosome uncoil
Cell undergoes cytokinesis and divides into 2 cells, 2 haploid cells created