6.2 The Stages of Mitosis Flashcards
What is mitosis?
Mitosis is the process of nuclear division by which two genetically identical daughter nuclei are produced that are also genetically identical to the parent cell nucleus (they have the same number of chromosomes as the parent cell)
What are the 4 stages of mitosis?
Prophase
Metaphase
Anaphase
Telophase
What happens during Prophase?
Chromosomes condense and are now visible when stained
The chromosomes consist of two identical chromatids called sister chromatids (each containing one DNA molecule) that are joined together at the centromere
The two centrosomes (replicated in the G2 phase just before prophase) move towards opposite poles
Spindle fibres (protein microtubules) begin to emerge from the centrosomes (consists of two centrioles in animal cells)
The nuclear envelope (nuclear membrane) breaks down into small vesicles
The nucleolus disappears
What happens during Metaphase?
Centrosomes reach opposite poles
Spindle fibres (protein microtubules) continue to extend from centrosomes
Chromosomes line up at the equator of the spindle (also known as the metaphase plate) so they are equidistant to the two centrosome poles
Spindle fibres (protein microtubules) reach the chromosomes and attach to the centromeres - this attachment involves specific proteins called kinetochores
Each sister chromatid is attached to a spindle fibre originating from opposite poles
What happens during Anaphase
The sister chromatids separate at the centromere (the centromere divides in two)
Spindle fibres (protein microtubules) begin to shorten
The separated sister chromatids (now called chromosomes) are pulled to opposite poles by the spindle fibres (protein microtubules)
What happens during Telophase?
Chromosomes arrive at opposite poles and begin to decondense
Nuclear envelopes (nuclear membranes) begin to reform around each set of chromosomes
The spindle fibres break down
New nucleoli form within each nucleus
