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cell divison
process where a single parent cell divides to form new daughter cells
diploid
have 2 indentical copies of each chromosome
haploid
one set of chromosomes, gametes are haploid
chromosome
sections of dna that are tightly coiled.
cell cycle
describe the different phases the cell is undergoing through its life
mitosis
process by which a parent cell form 2 diploid daughter cell
G0 phase
cell is fullfilling its function, not actively preparing for cell division
G1 phase
cell is starting to prepare for divison stimulated by growth factors/hormones. Lots of protein synthesis, organelles are copied
S phase
DNA replication occurs, centrosome is duplicated
G2 phase
the final growht, organelles are copied, copied dna is checked and mistakes are corrected
mitotic phase
last phase of cell cycle, stage where cell is actively dividing, 5 subphases
prophase
chromatin condense to chromatids, nuclear envelope breaks up, chromosomes attach at centromere forming sister chromosomes. Centrisomes at opposite ends of cell start forming spindle apparatus attached at the centromere
metaphase
spindle apparatus lines up the sister chromatids at the cells equator
anaphase
spindle apparatus fibers shortens--> The chromatids are pulled apart at the centromere and oriented towards each pole of the cell
telophase
spindle apparatus is broken down, new nuclear envelope begin to form around each set of chromosomes
cytokinesis
the cytoplasm is split in 2, actin pinches cytoskeleton in 2. 2 new diploid daughter cells have formed. New cell membrane is built. The cells goes into interphase again.
chromatin
uncoiled dna in the cell nucleus. Forms later chromosomes
sister chromatids
identical chromatids attached together at the centromere forming an x
centromere
binding together chromatids to sister chromatids. Where the spindle apparatus attach.
spindle apparatus
fibers that forms from the centrosomes attaching to the sister chromatids and pulling them towards each pole of the cell. a series of microtubels
centrioles
what the centrosomes are made up of
meiosis
process of which a diploid parent cell form 4 genetically unique haploid daughter cell. Cell division which is necessary for sexual reproduction creating gametes.
reduction division
cell division that results with a daughter cell with fewer chromosomes.
Meiosis 1
process which results in 2 haploid daughter cells which will undergo meiosis 2. Subphases= prophase 1, metaphase 1, anaphase 1, telophase 1 and cytokinesis
Prophase 1
nuclear envelope breaks down, chromatin condense to chromatids, centrisomes at each end of the cell from which spindle apparatus begins to form, homologous chromosomes start crossing over.
crossing over
process where homologous chromosomes can exchange dna, occurs during prophase 1. Enzymes facilitates the random clipping of section and those sections can then be transfered to the exact same location on the homologous chromosome. Creates diversity
homologous chromosomes
chromosomes in the same shape, size and genetic content. Ex one copy of chromosomes from each parent
metaphase 1
spindle apparatus attach at the paired homologous chromosomes and line them up at the cells equator
anaphase 1
the spindle apparatus fibers shortens causing the paired homologous chromosomes to be pulled apart to each pole of the cell. Sister chromatids are pulled toward opposite poles of the cell. How the homologous chromosomes is pulled apart is random which creates diversity.
telophase 1
spindle apparatus is broken down, nuclear envelope may/maynot form-chromatid may/may not decondense.
cytokinesis meiosis 1
the cytoplasm is divided into 2. Actin "pinches" the cell in half. New cell memebrane is built. 2 haploid daughtercells have formed that will go into meiosis 2.
meiosis 2
process of which a haploid cell will form 2 new haploid daughter cells
why is the daughter cells haploid
Each daughter cell contains a random mix of one chromosome from each homologue pair (one copy of each unique chromosome) but each chromosome is still attached to its no-longer-identical sister (and the chromosomes are linked as sister chromatids; no longer identical due to crossing over)
prophase 2
chromatin may condense into chromatid. Nuclear envelope may be broken down. Centrosoles is set at each pole of the cell. Spindle apparatus begins to form and attach to the not identical sister chromatids
metaphase 2
Spindle apparatus lines up the sister chromatids at the cells equator.
anaphase 2
as the spindle apparatus fibers shortens the sister chromatids is seperated and pulled apart towards each pole of the cell
telophase 2
the spindle apparatus is broken down, new nuclear envelopes begins to form around the new sets of chromosomes, chromatids decondenses into chromatin.
cytokinesis meiosis 2
cytoplasm is divided into 2. Actin piches the cell in half. New cell membrane is build. Process have resultet into 4 unique haploid daughter cells.
