2.2 - Eukaryotic Cell Cycle Flashcards
How Are New Cells Made?
The eukaryotic cell cycle describes the stages that a cell passes through to produce a new cell from a pre-existing cell
Before A Cell Can Divide It Must…
- grow in size and replicate its organelles
- duplicate its DNA and package chromatin in the form of chromosomes
- seperate chromosomes for exact distribution between two daughter cells
(These processes are coordinated by the cell cycle)
Two Key Phases Of The Cell Cycle
Interphase-
Is a period of normal functioning, growth and preparation for cell division
Includes the division of the nucleus (mitosis) and the cytoplasm (cytokinesis)
Mitosis-
Is a continuous fluid process that results in the division of the nucleus
(Cytokinesis occurs after mitosis and is the division of the cytoplasm to form two seperate cells)
Cytokinesis In Animal And Plant Cells
Animal-
A cleavage furrow forms and the cell pinches inward in half
Plant-
A cell plate grows outwards to divide the new cells
Binary Fission (Comparison Of Cell Division)
- prokaryotes
- singular circular chromosomes
- rapid
Mitosis (Comparison Of Cell Division)
- somatic cells of eukaryotes
- many linear chromosomes
- organelles must duplicate
- chromosomes must condense
- degeneration of the nucleus
- formation of spindle fibres
- reformation of the nuclear membrane
All Cell Division (Comparison Of Cell Division)
- are forms of cell division
- involve duplication of the genetic material
- result in two genetically identical daughter cells
- involve the reformation of the plasma membrane to seperate the newly formed daughter cells
Interphase
The stage between nuclear divisions and is a period of active growth (G1 Phase), synthesis of DNA (S Phase) and preparation for next division (G2 Phase)
Prophase
The chromatin threads condense and become visible as chromosomes held together by a centromere
Centrioles move to opposite ends of the cell (and microtubules radiate from them)
The nuclear membrane breaks down and the nucleolus disappears from view
Metaphase
Chromosomes, each made up of two chromatids move to the centre of the cell and line up along the equator
The centromere of each chromosome is attached to a spindle fibre
Anaphase
Spindle fibres attached to the centromere contract to their end of the cell and pull the chromosomes apart
Chromatids seperate at the centromere and move to opposite poles of the cell
Telophase
Chromosomes form tight clusters at each pole of the cell
Chromosomes de-condense as chromatin unwinds and becomes less visible
A nuclear envelope forms, nucleoli reform and the spindle dissembles
Cell membrane pinches inwards
Cytokinesis
The cytoplasmic division of a cell, bringing about the separation into two daughter cells
