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Genetic information is copied and passed onto daughter cells, The two…
Genetic information is copied and passed onto daughter cells
Mitosis
When a cell is not dividing the chromosomes are unwound single structure and are not visible = chromatin
At the beginning of cell division, chromatin condenses and coils tightly making it visible
Prophase
The chromosomes condense and become visible as two sister chromatids joined by a centromere. Centrioles migrate to the opposite sides of the cell (the poles). The spindle begins to form in animal cells only, made by the centrioles. The nuclear membrane disintegrates and the chromosomes scatter through the cell.
Metaphase
The spindle completes, and the microtubules go from one side of the cell to the other (from pole to pole). The chromosomes migrate to the equator of the cell and attach to the spindle fibres by the centromere. Each chromosome is attached to one spindle fibre.
Anaphase
the spindle fibres shorten pulling the chromatids to the poles of the cell by the centromeres. The centromere divides. Sister chromatids from one chromosome are pulled to opposite poles. At this point the chromatids are called chromosomes again
Telophase
The chromosomes reach the poles of the cell and uncoil. The spindle fibres break down. New nuclear membranes form around each set of chromosomes.
Plants
No centriole, but still has a spindle
The spindle is remains at telophase as the new cell wall is formed
Cytokinesis
Cells plates form between two new nuclei, developing into a new a cell wall
Cytokinesis
Cleavage furrow, cytoplasm indents
Produces two new genetically identical daughter cells, cells = same chromosome number as "Parent" cell
Used in asexual reproduction, Growth, Repair
Found in meristem tissue, roots, shoot tips.
Uncontrolled = Cancerous tumors
Chromosomes
Chromosomes are composed of DNA
Chromosomes are wound around histone proteins
Before cell division, DNA replicates leading to two identical DNA molecules joined by a centromere
Diploid
Paired (chromatid or chromosome)
Meiosis
Mitosis
Haploid
Unpaired
Mitosis
Interphase
G1
Cell size increase, Organelles replicate, Protein + ATP synthesis
S
DNA Synthesis
G2
repair, Growth
Meiosis
Genetic variation
Four daughter cells
Very similar to Mitosis
Meiosis 1
Differences
P1 - Chromosomes form bivalent pairs, chiasmata / crossing over
M1 - Pairs of homologous chromosomes line up, with independent assortment
Everything else is the same
Meiosis 2
A2 - Chromasomes pulled apart as chromatids
Everything else is the same as Mitosis
Cytokinesis
Forms two cells with a haploid nucleus
Two divisions
The two identical chromosomes = chromatids
Chromatids in one chromosome are called sister chromatids (Still identical)
Chromosomes in a pair = homologous pairs (Same size, shape, genes and same order)