Mitosis - Notes on Biology A Level OCR A PDF

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Notes on Biology A Level OCR A...

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Mitosis Early stage • During repulsion, chromosomes become more distinct  They curl  Shorten  Thicken  Obtain darker marks • Psychosomatic division • The nucleus becomes poor more noticeable than. Late stage • Chromosomes become more distinct and consist of two chromatids connected by the centromere. • Centrosomes move to opposite poles of the cell. • The nucleolus continues to shrink and disappear. • The nuclear shell disintegrates. Metaphase • Each centriole has a pole. • Pole centers develop / generate spindle fibers. • Axons attach to the centromeres of chromosomes. • Each centromere is attached to both poles. • Chromosomes are pulled towards the transposition or the equator. Anaphase • The fibers of the spindle contract. • Centromere division.

• Chromosomes (daughter chromosomes) are attracted to opposite poles of the cell. • The centromere is drawn first. • Each half-cell receives one chromosome from each chromosome. Telophase • Chromatids reach the poles of the spindle. • They begin to open. • They become less distinct. • Beginning of the reform of the nuclear hull. • Daughter chromosome Cytokinesis Cell division • In animal cells: o begins with constriction of cell edges • In plant cells: o has a cell wall. o Daughter cells have the same number of chromosomes and the same genetic makeup, and the parent cell - duplicates its DNA before mitosis. Mitosis Summary • DNA is replicated during interphase - NOT expected! Four stages: • First stage - the nuclear membrane disintegrates and the duplicated chromosomes condense, shorten and BEGIN to move towards the equator.

• Metaphase - the chromosomes line up along the equator attached to the axes by their centromere • Anaphase - the chromosomes of each duplicated chromosome are torn at the centromere and pulled around the different poles. • Telophase - chromosomes arrive at the poles and new nuclear membranes are formed, followed by the cytoplasmic - cytoplasmic process which actually separates to form two new daughter cells....